You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS REFERENCE TO RELATED PRIOR APPLICATIONS 
       [0001]    This application is a Continuation-in-Part of application Ser. No. 13/815,366 filed on Feb. 26, 2013 now abandoned which application claims priority pursuant to 35 USC 119 of Canadian application no. 2,769,963 filed on Feb. 27, 2012, the entire contents of said U.S. application Ser. No. 13/815,366 and said Canadian application no. 2,769,963 are hereby incorporated into the following application by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a support for a ladder when standing for use and more particularly to a support which may be attached and detached from a ladder and which has provision for adjustment of its location in order to provide the best support for a ladder. 
       BACKGROUND OF THE INVENTION 
       [0003]    A ladder which is in a position for use must be firmly supported for reasons of safety. Very often there is no place where the ladder can be placed where it will give access to where it is required while ensuring that it is adequately supported. For example, if a ladder is required to give access to a window in an upper storey of a building, the window may be adjacent to the corner of the building, it may be adjacent to a downspout or it may be wider than the width of the ladder itself. In these situations, it may be impossible to place the ladder to safely reach the window. 
         [0004]    If a ladder is required to give access to the soffit or fascia of a building or to a roof, the only support available is usually the gutter attached to the eaves of the building. Gutters are not intended for such use and rarely are strong enough to provide proper support for a ladder. Likewise, vinyl siding on a building is rarely strong enough to support a ladder and if a ladder is placed against it, the vinyl usually is dented by the weight of the ladder and becomes unsightly. 
       SUMMARY OF THE INVENTION 
       [0005]    I have invented a support for a ladder which can be placed where it will provide best support for the ladder. Briefly, the support of my invention includes a frame removably attachable to a ladder at preselected locations thereon such that when a ladder is standing for use, the elevation of the frame is adjustable. The frame is provided with contacting surfaces which are adapted to contact a stationary object for supporting the ladder. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]    The ladder support of my invention is described with reference to the accompanying drawings: 
           [0007]      FIGS. 1 and 2  are perspective views of the ladder support in conjunction with a conventional ladder; 
           [0008]      FIG. 3  is a perspective view of a rung connector of the ladder support; 
           [0009]      FIG. 4  is an elevation of the rung connector; 
           [0010]      FIG. 5  is a perspective view of a link of the ladder support; and 
           [0011]      FIGS. 6 and 7  are further perspective views of the ladder support. 
       
    
    
       [0012]    Like reference characters refer to like parts throughout the description of the ladder support. 
       DESCRIPTION OF PREFERRED EMBODIMENT 
       [0013]    With reference to  FIGS. 1 and 2 , the ladder support of the invention, generally  10 , is shown in conjunction with a conventional ladder, generally  12 . The ladder has longitudinal and transverse axes  12 , 13  respectively. A pair of vertical supports  14  run parallel to the longitudinal axis and rungs  15  run parallel to the transverse axis. 
         [0014]    The ladder support includes a frame, generally  16  having an outer arm  17 , a rung connector, generally  18  and a pair of links  20   a,b  which interconnect the outer arm and the rung connector 
         [0015]    With reference to  FIGS. 3 and 4 , the rung connector  18  includes an outer tube  22  which is composed of a pair of sections  22   a,b  movable longitudinally of each other in telescopic relationship to define a variable effective length. A conventional locking ring  24  when tightened prevents the sections from moving relative to each other. The outer tube and locking ring function as clamping means for the rung connector as is explained below. 
         [0016]    On each side of the rung connector is a U-shaped end wall  26  to which the outer ends of the outer tube are welded or otherwise attached. A rod  28  extends inwardly from each end wall. A sprocket  30  is welded or otherwise attached to the outer wall of each end wall. Its function is described below. 
         [0017]    Preferably, the end walls  26  are constructed so that they can be fastened firmly to the vertical supports of a conventional ladder intended for industrial use. The vertical supports of the ladder are generally channels and the rungs are tubular. Such a ladder is illustrated in  FIGS. 1 and 2 . In those illustrations, flanges  26   a  extend inwardly from outer webs  26   b  of the end walls The rungs are spaced apart about 1 foot and the flanges  26   a  are spaced apart slightly more than  3  inches so that the end walls fit snugly over the vertical supports of the ladder. The segments of rod  28  are arranged so that they fit into the hollows of the rungs of the ladder when the end walls fit over the vertical supports of the ladder. 
         [0018]    The end walls  26  are clamped or affixed to the rung of a ladder by means of outer tube  22 . As the end walls of the rung connector are pushed toward each in order to fit them over separate vertical supports of the ladder, the two segments of the outer tube slide toward each other. When no further inward movement is possible, the segments are immobilized by means of locking ring  24 . The end walls of the rung connector are then locked into engagement with the ladder. 
         [0019]    The outer tube and locking pin accordingly function to clamp the rung connector to the ladder. Since the rod can be inserted into any of the rungs of the ladder, the elevation of the rung connector is adjustable. The ladder support is accordingly adjustable on the ladder at preselected locations i.e. wherever this is a rung. 
         [0020]    With reference to  FIGS. 5 ,  6  and  7 , each link  20  is composed of a channel  50  to which a sprocket  52  is welded or otherwise attached to its inner end. The latter sprocket is sometimes referred to below as the “outer sprocket” and its teeth fit into the spaces between the teeth of sprocket  30 , sometimes referred to below as the “inner sprocket. The two sprockets are interconnected by a bolt (not illustrated) which extends through the end walls  26  of the rung connector, through the centre of the two sprockets  30 ,  52  and terminates at a threaded outer end to which a knurled knob  56  is threadably attached. 
         [0021]    The two sprockets and the bolt constitute a coupling for interconnecting the ladder to the rung connector. The coupling is adjustable because loosening of knob  56  allows the links to be separated from the rung connector thereby allowing the outer sprocket on the link to be rotated relative to the inner sprocket with resulting alteration of the angle of the links relative to the ladder. 
         [0022]    A fastener, generally  60 , interconnects the outer ends of the links and the outer arm  16  of the frame. The fastener consists of an limb  62  having one end pivotally connected to a hollow mount  64  secured to the top wall of the link and the other end removably received in an upwardly opening trough  66 . A removable pin  68  locks the limb in the trough 
         [0023]    Fastener  60  and the end outer edge  70  of the channel define a rectangular opening generally  72  for receipt of a rectangular hollow central tube  16   a  of the outer arm. The edges which define the opening are straight and contact the flat outer walls of the outer arm. Rotation of the outer arm is accordingly prevented as the arm slides in the opening. 
         [0024]    A pin  74  is vertically slidable relative to the fastener. The pin isposition to slide into and out of contact with the outer arm. When in contact with the outer end, the pin prevents the arm from sliding in opening  72 . 
         [0025]    Extending from each end of the central tube is a second rectangular tube  16   b  which has a smaller cross-section than the central tube and which, accordingly, is slidable in the hollow interior of the central tube. A third rectangular tube  16   c  fits into each end of second tubes. The tubes but may be immobilized by means of a number of thumb screws  84  spaced along the length of the arm. The effective length of the outer arm is accordingly variable because of the telescopic relationship of its components. 
         [0026]    A wheel  90  is mounted for rotation to the outer end of each third tube  16   c  and rotates about transverse axis  13 . Each wheel is horizontally spaced apart from the ladder and its circular outer wall  90   a  constitute a contacting surface which is adapted to contact a stationary object which supports the ladder. The stationary object will normally be the wall of a building but other objects may provide the necessary support. The wheels thus prevent the ladder from touching the wall or other stationary object when the ladder is standing for use. 
         [0027]    By means of the thus-described ladder support, the position of wheels  90  can be positioned where they will provide best support for the ladder. The angle of links can be adjusted by means of sprockets  30 ,  52  thereby permitting vertical adjustment of the wheels while the telescopic structure of the outer arm  16  permits horizontal adjustment of the wheels. 
         [0028]    It will be understood, of course, that modification can be made to the structure of the ladder support of the invention without departing from the scope and purview of the invention as defined in the appended claims.

Summary:
The support for a ladder has a frame which may be attached at various points on a ladder so that when the ladder is standing for use, the elevation of the frame is adjustable. The frame has an outer arm which extends parallel to the transverse axis of the ladder and outwardly from both of its sides. The arm is provided with two or more contacting surfaces which make contact with the stationary object which supports the ladder.