Abstract:
When golf is being played, the golf swing of a person ( 60 ) is decisive for the quality of the stroke. In order to obtain as good a golf swing as possible with a high hitting reliability and with precision, it is necessary to rotate the club with the arms ( 70 ) in a positionally fixed fashion about an imaginary axis through the head ( 68 ) and upper body ( 66 ). In order to monitor said positionally fixed rotation, it is generally necessary to consult a second person. Specifically, independent checking is possible only with difficulty. The object of the invention is therefore to provide a practice device ( 10 ) with which it is possible to check the position of the imaginary axis independently and without help from further persons in order to be able to practice the optimum golf swing even on one&#39;s own. 
     The object is achieved by a practice device ( 10 ) according to the invention. The practice device ( 10 ) has at least two lateral faces ( 18, 20 ) aligned substantially perpendicular to the underlying surface and with a distance between them that corresponds at least substantially to the human interocular distance. By positioning the practice device ( 10 ) on the underlying surface ( 28 ), it is therefore possible to visually determine even slight lateral deviations from a central ideal position above the practice device ( 10 ) by lateral faces ( 18, 20 ) that are correspondingly more or less visible.

Description:
STATEMENT OF RELATED APPLICATIONS 
     This patent application is the US Chapter II National Phase of International Application No. PCT/EP2011/003676 having an International Filing Date of 22 Jul. 2011, which claims priority on German Patent Application No. 10 2010 033 475.8 having a filing date of 5 Aug. 2010. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention relates to a practice device for checking the alignment, in particular, of a body part and/or a longitudinal axis of the body of a person. The invention further relates to the use of a practice device. Finally, the invention relates to a method for aligning, in particular, the longitudinal axis of the body and/or a body part of a person relative to an underlying surface. 
     2. Prior Art 
     When golf is being played, a golf ball is struck by a person, in particular a golfer, with the aid of a golf club. The so-called golf swing with which the golf club is moved by the person&#39;s use of his/her body relative to the golf ball is decisive for an accurately directed and successful execution of a strike. A good golf swing is distinguished in that the club is rotated with the aid of the arms, the shoulders and the upper body about an imaginary axis, the so-called longitudinal axis of the body through the head and backbone. It is largely undesired in this case for there to be a displacement of this axis during the golf swing, for example laterally or forward and/or back by movement of the upper body. 
     It is usual for the axis to be maintained during the golf swing by having a further person, such as a golf teacher, to monitor it by observing the golfer. This is required because the golfer himself has virtually no possibility to observe the alignment of his own body axis during his movement. It is therefore necessary in general to consult a second person for practice. It is therefore, in particular, impossible for him to improve his golf swing independently without the help of a third party. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a golfer with a practice device that can be easily handled and enables the golf swing to be practiced independently. 
     This object is achieved by a practice device for checking the alignment of a person, in particular a golfer, by the person him/herself and relative to an underlying surface, having a many-faced basic body with at least two lateral faces, and having means for setting up on an underlying surface, at least two of the lateral faces being aligned at least substantially perpendicular to an imaginary plane running through the setting up means, and the two lateral faces being arranged at a distance apart from each other that corresponds at least substantially to a human interocular distance. Accordingly, a practice device is provided that serves to check the alignment of a person, in particular a golfer, by the person him/herself. The alignment is undertaken relative to the practice device and/or to an underlying surface. To this end, the practice device has a many-faced basic body with at least two lateral faces. Also provided are means for setting up the practice device on an underlying surface. At least two of the lateral faces are aligned at least substantially perpendicular to an imaginary plane running through the setting up means. In the case of setting up on an underlying surface, said plane then runs at least substantially parallel to the underlying surface. Moreover, the at least two lateral faces are arranged at a distance apart from each other that corresponds at least substantially to an (average) human interocular distance. The at least two faces are arranged running perpendicular to an imaginary plane. Said plane corresponds to a horizontal plane for setting up on an underlying surface. The result of this is that the two lateral faces run perpendicular to the underlying surface. By virtue of the fact that the two lateral faces are at a distance from one another that corresponds approximately to a human interocular distance, a person can preferably respectively look with in each case one of his two eyes along respectively one of the lateral faces, that is to say with the left eye along a left-hand lateral face and with the right eye along a right-hand lateral face. In this position of the head and/or eyes, each of the two eyes is situated in the plane of each of the two lateral faces. Even slight deviations from this position can therefore easily be detected visually. Given increasing lateral deviations, instead of the upper edge of the lateral faces it is an increasing partial face of the lateral face that becomes visible. This is at least the case on the side of the practice device to which the head and/or the person has moved. Since the second eye does not simultaneously likewise move laterally next to, but first in the direction of the middle of, the practice device, it is a diminishing part of the surface of the corresponding lateral face or only the lateral edge that becomes visible there. Consequently, the necessary counter-movement in the other direction can easily be determined and undertaken in order to compensate the deviation from the central position. 
     It is preferred for the distance between the two lateral faces to correspond at least substantially to the interocular distance of the person using the device. In particular, the distance is between 5 cm and 8 cm. In particular, the distance is approximately 6.5 cm. A distance of 6.5 cm corresponds to the average interocular distance for humans. This is sufficient for most applications. However, since the interocular distance can vary among humans, the distance can be matched in particular to the interocular distance of the respective user. It is therefore further preferred for the distance between the two lateral faces to be of variable configuration. This can, for example, be achieved by a parallel displacement, in particular with the aid of a parallel feed, a screw gear or similar. It is thereby possible to set the distance appropriately depending on each user. Also considerable are practice devices with various distances for a user to select, or even customized versions of the practice device. 
     The practice device or the basic body preferably has several, in particular six, preferably eight outer faces. Furthermore, the practice device or the basic body of the practice device is designed to be in the shape of a polyhedron, a pyramidal frustum, a cuboid, a cube or the like, or has at least one basic shape corresponding thereto. Furthermore, at least one, preferably four, with particular preference six, and with further preference eight outer faces is/are present. At least two or preferably four of the outer faces are preferably designed as lateral faces. A top face and/or a bottom face are preferably present as outer faces. This corresponds exactly to the, in particular, six outer faces that, for example, are present in the case of a cuboid or cube. At least one of the outer faces, preferably however all the outer faces, is/are preferably designed as at least partially flat faces. It is further preferred to arrange the outer faces, in particular, opposite in pairs and/or parallel to one another. The outer faces thereby preferably form the outer walls or the outer boundary of the basic body. The bottom face preferably serves as means for setting up on the underlying surface. In particular, the lateral faces are arranged at least partially perpendicular to the setting up means, in particular to the bottom face and/or to the underlying surface. It is further preferred for the bottom face and/or the top face to be arranged at least substantially parallel to the underlying surface. 
     In particular, the lateral faces are designed as flat faces. The lateral faces are, in particular, designed as rectangular and/or square faces. It is further preferred for the lateral faces to be designed with color, preferably a single color, in particular homogeneously. This aim can be shared, for example, by signal colors such as, in particular, the colors red, yellow, blue or similar. It is preferred to select a color that stands out clearly from a normally used underlying surface. In the case of golf, the underlying surface is generally green grass or yellow sand of a golf course. Accordingly, the complementary color red can be effectively perceived. However, particularly for color-blind persons, for example, red-green blind persons, it is also possible to provide another coloration, in particular yellow and/or blue, which ensures as strong a contrast as possible with the underlying surface and with the remaining faces of the practice device. With further preference, a marking is arranged on the top face of the basic body, preferably centrally. By way of example, a bar, a line, a cutout or the like can serve as marking. The marking is preferably designed to be black. The line serves to indicate the middle of the basic body and/or the direction in which a user looks. The top face of the basic body is, with further preference, designed in a color that matches the underlying surface as far as possible, and/or preferably in green. 
     The practice device or the basic body is preferably assigned an alignment indicator. The alignment indicator can preferably be detachably connected to the basic body or practice device. For the purpose of connection to the basic body, a cutout, opening or holder is, in particular, provided therein. The connection between the alignment indicator and the practice device is preferably performed by screws, plugs or the like. The alignment indicator is preferably of T-shaped design. With further preference, the alignment indicator has several, in particular three preferably bar- and/or rod-shaped elements or bars. The elements can, in particular, be detachably connected to one another, in particular in the region of a coupling part such as a coupling sleeve. One bar serves to connect the basic body to the coupling sleeve. The remaining two bars are connected to the latter in a fashion that is mutually collinear and perpendicular to the end region of the bar, which is opposite the basic body. The two collinear bars are arranged perpendicular to said bar. 
     It is further preferred to provide two opposite outer faces, in particular a front face and a rear face of the practice device or of the basic body. In this case, the outer faces, in particular the front face and/or the rear face, preferably respectively have a cutout or notch. This notch is in particular of identical design for the front and rear sides. The notch is preferably designed in the shape of a wedge and/or a V. Consequently, the cross-sectional surface of the cutout is preferably of triangular design, in particular in the form of an equilateral triangle. The cutout is preferably arranged centrally on the corresponding face. With further preference, the cutout extends over the entire lateral face, preferably at least substantially in a vertical direction. This means, in particular, that the notch extends from the top face to the bottom face of the basic body. The cutouts and/or notches of two opposite lateral faces are preferably aligned running parallel to one another. The lateral faces of the notch that run together to a tip, that is to say the two partial faces thereof, therefore point toward the middle of the basic body. They are therefore aligned in a fashion opposite or opposed to one another. They preferably respectively point into the basic body. The cross section in a horizontal direction of the notch can, but need not, be constant. In particular the face size can vary given the same relationships. The notches or cutouts ensure that even a deviation of the positioning in the forward and backward directions can be determined by a person. The lateral deviations become visually detectable or measurable by the lateral faces being visible to the person more strongly or less strongly. The partial faces of the notch are visible to a different extent as a function of the relative position of the observer. If the observer or the person is situated further in the direction of the rear face of the basic body, the partial faces of the notch there are visible as relatively large areas compared to those of the notch of the front face. Consequently, counteraction can be taken by a displacement in the direction of the center of the basic body, that is to say in the direction of the front face. A positioning further in the direction of the front face correspondingly leads to a visibility over a larger area of the notch there, and to a corresponding remedy in the opposite direction. 
     Consequently, each of the notches and/or cutouts preferably has two preferably flat faces or partial faces. The partial faces preferably adjoin one another, in particular in the region of a common lateral edge. With further preference, the two adjoining partial faces are arranged at an angle to one another. The enclosed angle between the two lateral faces is preferably between 0° and 180°, preferably between 80° and 140°. In particular the angle is between 100° and 120° for optimum functioning, with further preference approximately 110°. Conversely, the angle enclosed between the partial face and the assigned outer face is preferably between 0° and 90°. In this case, it is preferred to propose between 30° and 40°, in particular approximately 35°, for optimum visibility. Preferably, an x-shaped marking is, in particular, provided on the top face of the basic body to improve the detectability of the x-shaped formation of said body. Said marking preferably extends diagonally between opposite corners of the top face. 
     In particular, the practice device and/or the basic body is designed completely or partially in one piece. A unipartite design ensures a very robust construction. On the other hand, the dismantleability is thereby reduced. Wood, plastics, metal and the like come into consideration as material. Combinations of various materials are also conceivable. 
     A use of a practice device according to the above-described configurations to check the alignment, in particular of a longitudinal axis ( 84 ) of the body and/or of a body part of a person ( 60 ) by the person ( 60 ) him/herself achieves the above-named object. The above statements relating to the practice device are likewise valid here in principle. Consequently, a practice device corresponding to the above statements is used to check the alignment, in particular, of the longitudinal axis of the body and/or of a body part of a person by the person him/herself. Consequently, the person can be positioned, or position him/herself, relative to the practice device and, if appropriate, independently detect deviations from the ideal position. The ideal position is considered to be a position that can be determined upon setting up the practice device on an underlying surface with lateral faces running at least substantially perpendicular to the underlying surface. In the ideal position of the person, the person is standing with both legs equally spaced apart from the practice device on different sides. The upper body is slightly angled forward. The eyes are respectively simultaneously positioned vertically above one of the lateral faces of the basic body. In this case, the left eye is situated in the plane of the left-hand lateral face, while the right eye is situated in the plane of the right-hand lateral face. This can be verified from the fact that neither of the two lateral faces, or a portion thereof that is as small as possible, is visible. A laterally deviating positioning leads to a (stronger) visibility of the lateral face in which the displacement has taken place. If one eye of the person is situated to the left of the left-hand lateral face, the latter is at least partially visible, while the right-hand lateral face is not visible at all or much less so. If the interocular distance corresponds to the distance between the lateral faces of the practice device, the person does not see the two lateral faces at all, or sees only the lateral edge thereof, if it is ideally positioned above the lateral faces with the respective eyes. In order to improve the alignment, it is therefore necessary to move away to the other side from the side whose lateral face is visible in general or at least visible to a larger extent than the other lateral face. Should the two lateral faces be simultaneously visible to a slight extent even given the ideal or central position, the interocular distance of the person is greater than the distance between the lateral faces. It is then necessary to ensure that the visible area of the two lateral faces is minimized for an ideal alignment. If the interocular distance is smaller than the distance between the lateral faces, an inaccuracy arises in the extent to which the person&#39;s head can move between the two planes of the lateral faces without one of the eyes being able to look laterally onto the face. It follows that there can be no visual alignment with the lateral faces in this region. Consequently, it is possible to conceive of the possibility of setting the distance between lateral faces or, alternatively, to conceive of an, if appropriate, personalized configuration of the practice device in the case of which the distance between the lateral faces is matched to the distance between the eyes of the user or the person in an individual fashion. Again, it is possible to select a suitable practice device from a number of prefabricated practice devices with different distances between the lateral faces. 
     A method for aligning a person relative to an underlying surface, namely, a method for aligning a person, in particular a golfer, relative to an underlying surface, with the aid of a practice device or the basic body thereof, as disclosed herein, in which at least one, preferably two lateral faces of the practice device are aligned at least substantially perpendicular to the underlying surface, in which the lateral faces become visible to the person to a different extent as a function of the position of the eyes of the person relative to the practice device achieves the above-named aim. In accordance therewith, the person, in particular a golfer, can be aligned, or can align himself, with the aid of a practice device in accordance with the above statements. To this end, the practice device has at least one, preferably two lateral faces, which are aligned at least substantially perpendicular to the underlying surface. Moreover, the lateral faces become visible to the person to a different extent as a function of the position of the eyes of the person. Depending on the positioning of the eyes, this means that the lateral faces become detectable not at all, or, as a function of the lateral deviation from the ideal position, to a corresponding extent as a surface that is more visible or less visible. The person can be moved in an opposite direction in order to compensate the deviation thus detected. To this end, the person or, correspondingly, the head or the upper body thereof, must be moved in the corresponding other direction away from the visible lateral face. 
     The lateral faces are more preferably simultaneously viewed with in each case one of the two eyes of the person. One of the two eyes is situated for this purpose in the plane of one lateral face, while the other eye is arranged in the plane of the other lateral face. This corresponds to the ideal position of the head of the person above the practice device or the basic body. The person is more preferably aligned in such a way that he/she looks with one eye along a first lateral face, and with the second eye along the second lateral face. In particular, to this end the basic body can be set up, or positioned relative to an underlying surface, in such a way that each eye of the person is respectively situated in one of the planes of the lateral face, preferably above the basic body, there preferably being a perpendicular arrangement of the planes relative to the underlying surface. It is thus ensured that the alignment can be performed by the person. To this end, the feet of the person are placed in such a way on both sides at the same distance from the practice device that the axis runs through the head and upper body, the longitudinal axis and upper body, in a perpendicular plane relative to the underlying surface. However, because of the foot position spaced apart from the basic body, the axis is inclined forward. 
     In particular, the visibility of the two lateral faces is simultaneously minimized in that a longitudinal axis of the body of the person is suitably displaced. In this case, a simultaneous aiming is preferably taken with in each case one eye along in each case one of the lateral faces. This corresponds to the arrangement of the eyes in one of the planes of the lateral face. A deviation, its extent and its direction can be detected visually at once by a simultaneous observation of the two lateral faces. A simultaneous minimization of the visible faces of two, preferably all the outer and lateral faces and/or partial faces is attempted for the optimum alignment of the person. 
     The practice device or the basic body is more preferably positioned, put down or laid down on the underlying surface, preferably with a bottom face. To this end, the bottom face is designed as setting up means and preferably designed to be at least virtually or partially flat. The bottom face or its contact points with the underlying surface are therefore arranged at least virtually parallel to the underlying surface. At least two lateral faces of the practice device are more preferably arranged at least substantially perpendicular to the underlying surface. The two lateral faces are aligned at least virtually parallel to one another. A distance between the lateral faces that corresponds to the mean or average interocular distance of a or the person is more preferably provided. This distance is preferably between 5 cm and 8 cm, preferably approximately 6.5 cm. 6.5 cm is known as the average human interocular distance. In general, this average distance suffices for the alignment. In particular, adjustability can be provided for the exact matching to a user, or alternatively it is possible to undertake a customized finishing of the practice device. In particular, the distance can also be set variably as a function of the interocular distance of the user or the person. 
     In particular, the practice device is put down on an underlying surface in such a way that the preferably parallel lateral faces are arranged at a preferably right angle to the underlying surface. The feet of the person are more preferably respectively positioned with the same distance between them laterally in the plane of the respective lateral face. In particular, the center is arranged between the eyes of the person perpendicularly above the practice device, or is arranged there such that the lateral faces are preferably not visible to the person or not visible to the same extent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred exemplary embodiments of the invention are described in more detail below with the aid of the drawings, in which: 
         FIG. 1  shows a perspective view of a first exemplary embodiment of the invention, 
         FIG. 2  shows a front view of the first exemplary embodiment, 
         FIG. 3  shows a side view of the first exemplary embodiment of the invention, 
         FIG. 4  shows a plan view of the first exemplary embodiment, 
         FIG. 5  shows a perspective view of a second exemplary embodiment of the invention, 
         FIG. 6  shows a front view of the second exemplary embodiment, 
         FIG. 7  shows a side view of the second exemplary embodiment, 
         FIG. 8  shows a plan view of the second exemplary embodiment, 
         FIG. 9  shows a plan view of a third exemplary embodiment of the invention, 
         FIG. 10  shows a sectional view of the front face of the third exemplary embodiment, 
         FIG. 11  shows a side view of a person in the case of the observation of the third exemplary embodiment of the invention, and 
         FIG. 12  shows a plan view in accordance with  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1 to 4  show a practice device  10  as a first exemplary embodiment of the invention. In this case, the practice device  10  comprises in practice only a basic body  12 . 
     This basic body  12  is designed in the shape of a cube. The basic body  12  accordingly has six outer faces  14 . The outer faces  14  are of identical area and shape in this case. Square faces are involved in each case. Moreover, the outer faces  14  are of flat design. 
     In each case two of the outer faces  14  are arranged parallel to one another on opposite sides of the basic body  12 . A lateral edge  16  is situated where two of the outer faces  14  meet at the edge. As a cube, the basic body  12  has twelve of these lateral edges  16 . The two outer faces  14  meeting at one of the twelve lateral edges  16  are respectively designed in this case in a fashion running perpendicular to one another. 
     Two of the outer faces  14 , specifically the left-hand lateral face  18  and the right-hand lateral face  20  running parallel thereto, are colored for better visibility. To this end, they have an all-over homogeneous coloration. A red coloring of the lateral faces  18  and  20  stands out particularly well in this case against, for example, a green underlying surface of grass. Alternatively, another color can be selected, for example for color-blind users. In each case, the two lateral faces  18  and  20  can be colored the same or purposely differently. 
     The front or rear outer face  14  respectively adjoining the lateral faces  18  and  20  is also denoted as front face  22  or as rear face  24 , respectively, because of its arrangement. To improve visibility, they are likewise colored homogeneously with a color generally deviating from the color of the lateral faces  18  and  20 . A vibrant color such as yellow or blue, for example, is suitable for this. Alternatively, it is also possible to provide the same coloration for all lateral outer faces  14 , that is to say the lateral faces  18  and  20 , the front face  22  and the rear face  24 . 
     The bottom outer face  14  is designed as the bottom face  26 . The practice device  10  stands on an underlying surface  28  with this bottom face  26 . The bottom face  26  therefore serves as means for setting up on the underlying surface  28 . Because of the partially perpendicular arrangement of the outer faces  14  relative to one another, the lateral faces  18  and  20 , as well as the front face  22  and the rear face  24 , stand perpendicularly or vertically on the bottom face  26  and thus the underlying surface  28 . The upper outer face  14  designed as top face  30  is correspondingly arranged parallel to the bottom face  26  and thus also parallel to the underlying surface  28 . To improve visibility, the top face  30  and, if appropriate, also the bottom face  26  are provided with a color deviating from the remaining outer faces  14 . 
     The top face  30  has an, in particular black, marking  32  in the center of the face. The marking  32  is designed as a straight stripe, bar, line, or else as a cutout. In this case, it runs in the direction from the top lateral edge  16  of the front face  22  to the top lateral edge  16  of the rear face  24 . In this case, it marks the middle between the top lateral edge  16  of the lateral face  18  and the top lateral edge  16  of the lateral face  20  or the left and right lateral edges  16  of the top face  30 . The direction in which a user looks usually runs along this marking  32 . 
     The second exemplary embodiment of the invention is illustrated in  FIGS. 5 to 8 . Here, as well, the practice device  10  has a basic body  12 . It is chiefly only the deviations as contrasted with the first exemplary embodiment that are described below, since the basic construction is at least similar. 
     The basic body  12  of the second exemplary embodiment likewise shows a basic cubic shape. Here, at least parts of the outer faces  14  are arranged on the surface of a cube. In the region of the front face  22  and the rear face  24 , however, notches  34  and  36  are present here. These notches  34  and  36  run respectively in perpendicular or vertical fashion when the practice device  10  is set up with the bottom face  26  on an underlying surface  28 . The notches  34  and  36  recede into the interior of the basic body  12  from the respective parts of the front face  22  and of the rear face  24 . They therefore extend from the outer faces  14  into the basic body  12 . Consequently, two additional partial faces  38  and  40  are respectively provided as lateral bounding faces of the notches  34  and  36 , respectively. The notches  34  and  36  are designed overall in the shape of a V or a wedge. The angles at which the partial faces  38  and  40  respectively run in a fashion angled away from the front face  22  and the rear face  24  are identical in this case for all four partial faces  38  and  40 . Thus, the partial faces  38  and  40  also have the same surface area. They are designed as flat, rectangular faces. 
     In the region of the top face  30  and the bottom face  26 , the notches  34  and  36  respectively penetrate the two faces. It is true that the basic surface of the top face  30  or of the bottom face  26  is square as previously. However, the two faces are not designed as square faces. Specifically, because of the wedge-shaped notches  34  and  36 , in each case sections which are triangular at the edges thereof are provided in the region between the lateral edges  16  and the front face  22  and the rear face  24 . It follows that the lateral edges  16  run partially in the region of the lateral faces  18  and  20  and respectively run along said square basic surface in the region of the front face  22  and the rear face  24 . Only the partial faces  38  and  40  cut out equilateral triangular parts from the top face  30  and also from the bottom face  26 . The lateral edges  16  therefore run along the triangular cutouts in this region. 
     Partial faces  38  and  40  enclose an angle of approximately 110° here. This corresponds to an angle of approximately 35° between each of the partial faces  38  and  40  in the case of each of the notches  34  and  36 , and the front face  22  or the rear face  24 . 
     In the view of the front face  22  in accordance with  FIG. 6 , it is to be seen that the four surfaces to be recognized in this view, specifically the left-hand part of the front face  22 , the partial faces  38  and  40  and the right-hand part of the front face  22 , are designed at approximately the same width in the frontal view. However, it is also conceivable to change the relationship of the width of the notch  34  or  36  relative to the edge regions  14 ,  22 . The edge regions or sections of the front face  22  should, however, be designed with equal width in each case, just as should the two partial faces  38  and  40 . This ensures that a central arrangement of the notches  34  and  36  results, on the one hand, and, at the same time, the notch  34  or  36  is a triangular equilateral basic shape or cross-sectional area of the cutout wedge. The above is true both for the front face  22  and, correspondingly, for the rear face  24 , which is designed in a fashion virtually identical to the first. In the plan view according to  FIG. 8 , the top face  30 , and therefore the entire basic body  12 , consequently has a shape that might be called an X shape. Consequently, the exemplary embodiment shown here is also denoted as an “X-cube”. 
     The third exemplary embodiment of  FIGS. 9 and 10  is based on the first exemplary embodiment shown in  FIGS. 1 to 4 . Consequently, as shown here, the basic body  12  of the practice device  10  is designed to be virtually identical to that of the first exemplary embodiment. Alternatively, by way of example, it is also possible, however, to replace the basic body  12  with the basic body  12  of the second exemplary embodiment, or other alternative designs of the invention. The changes described below are then to be undertaken as appropriate. 
     The basic body  12  is therefore of cubic design here. Connected thereto is an alignment indicator  42 . Said alignment indicator  42  is substantially designed in the shape of a T. To this end, three bars  44  and  46  are interconnected. The two bars  46  are interconnected and connected to the bar  44 , perpendicular to them, by means of a coupling sleeve  48 . The two bars  46  are aligned collinearly with one another. The bars  44  and  46  are preferably plugged or screwed into the coupling sleeve  48 . To this end, the coupling sleeve has three holders or openings  50  with preferably corresponding internal threads. The bars  44  and  46  correspondingly have external threads corresponding to these internal threads. They can therefore be screwed into the coupling sleeve  48 . Alternatively, it is also possible to provide a for example latchable plug connection. 
     The end of the bar  44  that is opposite the coupling sleeve  48  can be connected to the basic body  12 . To this end the basic body  12  has a holder or opening  52 . The bar  44  can be plugged or inserted into this opening  52 . An external thread corresponding to an internal thread in the opening  52  is arranged at the end region of the bar  44  for the purpose of particularly stable holding. The bar  44  can therefore be screwed into the basic body  12 . However, as an alternative, it is also possible here to provide an in particular latchable plug connection or the like. The opening  52  is arranged at the bottom region of the front face  22  of the basic body in the vicinity of the bottom lateral edge  16  relative to the bottom face  26 . Moreover, the opening  52  is provided centrally between the two lateral faces  18  and  20  in the bottom region of the front face  22 . Consequently, the alignment indicator  42  lies overall at least substantially flat on the ground or underlying surface  28  when it is connected to the basic body  12  and the latter is set up with its bottom face  26  on the underlying surface  28 . 
     Owing to the screwing means, which can as an alternative also be designed as a plug system, the alignment indicator  42  can be dismantled and therefore easily transported. By arranging a corresponding opening  52  in the region of the notch  34  of the basic body  12 , for example, of the second exemplary embodiment, the alignment indicator  42  can also easily be combined with said second exemplary embodiment, or else with further alternative designs of the invention. 
     With the aid of  FIGS. 11 and 12 , the practice device, its method of operation, the use of the practice device and the corresponding method are described below: 
     The description is undertaken with the aid of a practice device according to the third exemplary embodiment of the invention. The cubic basic body  12  to which the alignment indicator  42  is connected is thereby provided. As described above, the T-shaped alignment indicator  42  has a bar  44  and two collinear bars  46  that are perpendicular thereto. A coupling sleeve  48  serves to connect said bars. The practice device  10  with basic body  12  and alignment indicator  42  is arranged lying on the underlying surface  28 . Consequently, the bars  44  and  46  run at least substantially parallel to the underlying surface  28 . 
     A person  60  is sketched in  FIGS. 11 and 12  in order to explain the use and the method. The person  60  is standing with his/her two feet  62  on the underlying surface  28 . Two legs  64  aligned substantially vertically support in this case an upper body  66  that is angled away slightly forward or in an inclined manner. The upper body  66  is inclined forward in such a way that a head  68  of the person  60  is situated substantially above the basic body  12  of the practice device  10 . In particular, two eyes  70  in the head  68  of the person  60  are positioned above the basic body  12 . 
     The person  60  can be a golfer. Consequently, with his/her arms  72  the person  60  holds a golf club  74  in a fashion directed obliquely downward in the direction of the underlying surface  28 . A club head  76  of the golf club  74  is situated in this case at the level of and next to a golf ball  78 . As is usual, the golf ball  78  is laid onto a small peg  80 , the so-called “tee”, that is plugged with a pointed end into the underlying surface  28 , for example a grassy area of a golf course. 
     In order to explain the alignment of the head  68  above the basic body  12 ,  FIG. 11  shows a dashed line  82  that runs perpendicular to the underlying surface  28  and simultaneously marks the direction in which the eyes  70  are looking. The feet  62  of the person  60  are placed on the side of the two bars  46  averted from the basic body  12 . In this case, the bar  44  or the coupling sleeve  48  is situated substantially on a central line between the two feet  62 . Owing to the slightly forward inclination of the upper body  66 , the head  68  of the person  60  runs above the basic body  12 . The feet  62  are placed at the same distance respectively left and right of an imaginary extension of the bar  44  beyond the coupling sleeve  48 . As a result of this, the upper body  66  is aligned with a longitudinal axis  84  of the body, which runs along the bar  44 , in a vertical plane in a longitudinal direction of the valve  44  when the head  68  of the person  60  is situated centrally above the basic body  12  (see  FIG. 12 ). As soon as the head  68  moves, for example, laterally in the direction of one of the lateral faces  18  or  20 , the longitudinal axis  84  of the body is no longer situated in the same vertical plane with the bar  44 . The aim is to avoid and/or correct these disadvantageous, lateral deviations that occur during a golf swing for executing a strike with the golf club  74 . 
     The person  60  can now easily check the correct or ideal position or alignment of the longitudinal axis  84  of the body: to this end, the basic body  12  has a transverse dimension or a distance between the lateral faces  18  and  20  that precisely corresponds to the interocular distance of the two eyes  70  of the person  60 . This is illustrated in  FIG. 12 . Given an ideal alignment, on the one hand, the person  60  respectively looks with one of the eyes  70  onto each of the two lateral edges  16  of the lateral face  18  or lateral face  20 . It follows that the person perceives the respective lateral face  18  or  20  only as a line in the form of the lateral edge  16 . Given an ideal alignment, on the other hand, the feet  62  are arranged at the same distance apart on in each case one side of the plane of the bar  44 . Moreover, they are positioned in a fashion distanced from the basic body  12 , in particular on the side of the bars  46  that is averted from the basic body  12 . The longitudinal axis  84  of the body therefore runs through the upper body  66  and head  68  in one plane with the bar  44 . 
     In order to amplify the visual effect, the lateral faces  18  and  20  are designed in a color standing out clearly from the underlying surface  28 . Since the underlying surface  28  is usually a grassy area, an intensive color, such as the color red, is frequently provided in this case. The marking  32  on the top face  30  of the basic body  12  serves in all cases to indicate the lateral center of the basic body  12 . It can serve as a further reference point for the alignment of the person  60 . 
     As soon as the head  68  moves laterally in one direction, the corresponding eye  70  comes with its viewing direction next to the basic body  12 . Owing to the lateral positioning, the person  60  can look obliquely from above onto the lateral faces  18  and  20  with the aid of the eye  70  situated laterally next to the basic body  12 . The lateral face  18  or  20  is now no longer perceptible as a line, but as a surface becoming larger with increasing lateral deviation. 
     In order to correct the alignment of the longitudinal axis  84  of the body, the person  60  need only determine which of the two eyes  70  perceives one of the two faces  18  and  20  as a surface, or which eye  70  perceives a relatively large area. A lateral deviation from the center of the basic body  12  outward therefore exists in the direction of the eye  70  that perceives the relatively large lateral face  18  or  20 . To correct this deviation, the person  60  must move with his/her head  68  in accordance with the upper body  66 , therefore in an opposed direction. This therefore means that when the left eye  70  perceives a relatively large part of the lateral face  18  than does the right eye  70  of the lateral face  20 , the person  60  must move to the right in the direction of the lateral face  20  in order to correct this deviation. A corresponding statement holds in the opposite case when the perception of the right-hand lateral face  20  is greater than that of the left-hand lateral face  18 . The person  60  must then move correspondingly to the left in the direction of the lateral face  18 . 
     The notches  34  and  36  of the second exemplary embodiment can serve also to be able to perceive a deviation of the positioning of the longitudinal axis  84  of the body from the ideal position in the direction parallel to the bar  44 . Owing to the partial faces  38  and  40  which run completely inward in relation to the front face  22  and the rear face  24 , given a positioning of the eyes  70  in a line with the middle between the lateral edges  16  of the front face  22  and the rear face  24 , the person  60  sees the partial faces  38  and  40  as areas of the same size. 
     As soon as the head  68  moves upward or downward along the direction of the bar  44  in the plane of the sheet, that is to say forward or rearward, thus in the direction of the front face  22  or the rear face  24 , as seen by the person  60 , there is a change in the perceived areas of the partial faces  38  and  40 . The result of a forward movement is that the partial faces  38  and  40  of the rear face  24  of the basic body  12  are visible as larger areas than those of the front face  22 . This is correspondingly the other way around given a rearward movement. Consequently, the practice device  10  can be used to determine whether the longitudinal axis  84  of the body is optimally aligned for carrying out a strike when playing golf. This can respectively be done even by the person  60  himself without the aid of a third party. 
     LIST OF REFERENCE NUMERALS 
     
         
           10  Practice device 
           12  Basic body 
           14  Outer face 
           16  Lateral edge 
           18  Lateral face 
           20  Lateral face 
           22  Front face 
           24  Rear face 
           26  Bottom face 
           28  Underlying surface 
           30  Top face 
           32  Marking 
           34  Notch 
           36  Notch 
           38  Partial face 
           40  Partial face 
           42  Alignment indicator 
           44  Bar 
           46  Bar 
           48  Coupling sleeve 
           50  Opening 
           52  Opening 
           60  Person 
           62  Foot 
           64  Legs 
           66  Upper body 
           68  Head 
           70  Eyes 
           72  Arm 
           74  Golf club 
           76  Club head 
           78  Golf ball 
           80  Peg 
           82  Line 
           84  Longitudinal axis of the body