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: 
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a structure which can be placed in a compact storage mode which is suited for transport and which, at a chosen site, can be converted with relative ease into an enclosure. 
       SUMMARY OF THE INVENTION 
       [0002]    The invention provides a structure which includes a base of rectangular outline with a lower surface which faces the ground and an upper surface, first and second ends which are fixed to the base, which are spaced apart and which extend vertically, and at least a first assembly which has a first side with an inner surface and an outer surface, a second side which opposes the first side, a panel fixed to and extending between the first side and the second side, a first wall fixed at least to the first side and the panel, a second wall which is spaced from and which opposes the first wall and which is fixed at least to the first side and to the panel wherein the first assembly is attached and is pivotally movable relative to the base between a compact configuration at which the panel overlies the upper surface of the base, the first wall is substantially adjacent the first end and the second wall is substantially adjacent the second end and an operative configuration at which the outer surface of the first side faces the ground, the panel extends generally vertically, the first and second walls are displaced, respectively, from the first and second ends, and the second side is positioned above and opposes the inner surface of the first side. 
         [0003]    In order to move from the compact configuration to the operative configuration the first assembly may be pivoted relative to the base through approximately 90°. 
         [0004]    The structure may include a second assembly, of generally similar shape to the first assembly, which is pivotally secured to the base. When the first assembly is moved to the operative configuration the second assembly, which is in a compact configuration, may then be movable to a respective operative configuration. With both assemblies in the respective compact configurations, the first assembly, which is generally similar in shape to the second assembly but which has a larger overall dimension, overlies at least a greater part of the second assembly. 
         [0005]    With each assembly in a respective operative configuration, a space above the upper surface of the base may be closed by roof structure. 
         [0006]    With each assembly in a respective compact configuration the structure is effectively similar in shape and size to a conventional shipping container. To enable an interior of the structure, in this mode, to be accessed, at least the first end may include an aperture e.g. a doorway or window which is positioned so that it is in register with openings in respective sides of the two assemblies which are adjacent the first end. Each opening may, itself, define a respective doorway or a window. 
         [0007]    The structure may include guides which guide the movement of the first wall and of the second wall relative to the first end and to the second end respectively, as movement between the compact and operative configurations takes place. 
         [0008]    Similarly the second side may be movable in a controlled and limited way relative to the panes so as to take up a desired slope (roof forming) in the operative configuration. Additionally it may be necessary to guide the second side so that it can be moved without hindrance i.e. so that it can be moved between respective positions in the compact configuration and the operative configuration without corning into contact with or otherwise snagging any part of the structure or equipment which may be positioned inside the structure in such a way that effective movement is prevented. 
         [0009]    The first wall may include a locking member which is engageable with a complementary locking member on the first end to brace the structure, particularly when the structure is in the compact configuration. 
         [0010]    Gaps between the first end and the first wall may be sealed by means of suitable seals which may be of an elongate U-shape. These seals may be interlocking. Additionally these seals may act as locks which mechanically firmly secure different components of the structure together in a rigid and stable manner. 
         [0011]    Each assembly may be movable in any appropriate manner relative to the base, for example by means of hydraulically activated devices. Use may be made of piston and cylinder assemblies and, conveniently, in each assembly the respective first and second walls may be designed to be sufficiently thick so that there is adequate space inside an enclosed volume to accommodate such piston and cylinder assemblies or any equivalent mechanism. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention is further described by way of example with reference to the accompanying drawings in which: 
           [0013]      FIGS. 1 to 9  illustrate somewhat schematically successive stages in the deployment of a structure according to the invention as it is moved from a compact configuration to an operative configuration, 
           [0014]      FIG. 10  illustrates various constructional details on the structure, and 
           [0015]      FIG. 11  depicts a structure according to a variation of the invention which includes doors and windows. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0016]      FIG. 1  of the accompanying drawings illustrates in perspective a structure  10  according to the invention in a compact, storage and transport configuration.  FIGS. 1A and 1B  show respectively the structure schematically in cross-section on transverse planes. 
         [0017]    The structure  10  includes a base  12  which, in plan, is rectangular in outline, and which has an upper surface  12 A and a tower surface  12 B which faces towards the ground. The structure  10  has a first end  14  and a second end  16  which is spaced from and which opposes the first end  14 . The ends  14  and  16  are at respective opposed edges of the base  12 . Each end  14  extends vertically. 
         [0018]    Secured to the base  12  are a first assembly  18  and a second assembly  20 . 
         [0019]    The first assembly  18  has a first side  22 , a second side  24  which is spaced from and which is generally parallel to the first side and a bridging panel  26 . The first side  22  has an outer surface  22 A and an inner surface  22 B. With the structure  10  in the compact configuration the first side  22  is vertical and has a lower edge  22 C which is attached by means of a hinge joint  30  to an adjacent longitudinal edge  12 C of the base  12 . The panel  26 , which extends between upper extremities of the first side  22  and the second side  24 , overlies the upper surface  12 A of the base  12 . 
         [0020]    The assembly  18  has opposed first and second walls  34  and  36  respectively which are closely spaced from and which are generally parallel to opposing surfaces of the first and second ends  14  and  16 . 
         [0021]    The second assembly  20  is generally similar to the first assembly  18 . The second assembly has a first side  42 , a second side  44  which opposes the first side  42 , a bridging panel  46  at opposed extremities of the first and second sides, a first wall  54  and an opposing second wall  56 . The second assembly  20  is sized so that, as is shown particularly, in  FIGS. 1A and 1B , with the structure  10  in the compact configuration, the second assembly  20  is nested closely inside the first assembly  18 . The second assembly is pivotally connected by means of a hinged joint  60  along a lower edge of the first side  42  to a corresponding longitudinal edge of the base  12 . 
         [0022]      FIGS. 2 to 9  illustrate how the structure  10  is converted from the compact configuration shown in  FIG. 1  into an operative configuration. The structure in the compact configuration is positioned on a chosen site. The lower surface  12 B of the base may rest on the ground or it may be supported above the ground on suitable legs, not shown. In an initial step, shown in  FIG. 2 , the first assembly  18  is pivoted about the hinge  30  in a clockwise direction  62  through about 90° so that the outer surface  22 A of the first side  22  is brought into ground-engaging contact. The panel  26  is thereby moved from a horizontal orientation to a generally vertical orientation. The second side  24  is moved from a vertical orientation to a position, see  FIG. 3 , at which the second side  24  vertically overlies the first side  22 . At this point the first side  22  is generally co-planar with the base  12 . 
         [0023]    The second side  24  is attached to the panel  26  by means of a pivotal connection  64  which interconnects abutting edges of the first side  22  and the panel  26 . This pivotal connection permits the second side  24  to be raised to an inclined position, as is shown in  FIG. 3 , at which an upper surface  24 A of the second side is inclined to the horizontal. 
         [0024]      FIG. 4  shows the first assembly  18  fully displaced from the base and in an operative position. 
         [0025]    The aforementioned movement of the first assembly  18  exposes the second assembly  20  so that it is then possible to pivot the second assembly  20  about the pivot connection  60  in an anti-clockwise direction  66 . The procedure which is followed is substantially the same as what is followed for moving the first assembly  18  to the operative mode. Thus, as is shown in  FIGS. 5, 6 and 7 , the second assembly  20  is pivoted to bring the first side  42  into ground-engaging contact. The first side  42  is then generally coplanar with the base  12 . The panel  46  is moved to a vertical orientation and the second side  44  is thereby positioned above an upwardly facing surface of the first side  42 . The second side  44  is slightly pivoted upwardly so that an upper surface  44 A of the second side slopes relative to the horizontal. 
         [0026]      FIG. 7  shows a gap  70  between an edge  44 B of the second side  44 , and an opposing edge  24 B of the second side  24 . This gap can be closed in various ways. As is shown in  FIG. 8  extension pieces  24 X and  44 X projecting respectively from the sides  24  and  44 , are moved towards each other, in order to form a roof  74  from the sides  24  and  44  and the extension pieces  24 X and  44 X. The roof has an apex  76 . Closures  74 X, on one side of the structure and  74 Y (not visible in  FIG. 8 ) on an opposing side of the structure, are then used to close respective openings adjacent the apex  76 . 
         [0027]    If the structure is to be returned to the compact storage configuration shown in  FIG. 1 , the preceding sequence of operations is reversed. The second assembly  20  is first pivoted into a storage configuration whereafter the first assembly  18  is pivoted into a storage configuration at which it overlies and closely encloses the second assembly. 
         [0028]    An advantage of the construction which has been described is that conversion from one mode to the other mode is readily effected. The operative configuration defines an enclosure which is bounded above and below, and on four sides, by rigid elements. In the compact configuration those elements which form the sides and roof (in the extended configuration) are positioned close to one another so that an enclosed volume which is usable for storage purposes is defined. This is evident from an inspection of  FIGS. 1A and 1B , in particular. 
         [0029]    In the preceding description the nature of the structure has been described generally in a schematic manner. Some constructional details which are necessary for an effective implementation of the invention are shown in  FIGS. 10 and 11 .  FIG. 10  illustrates an inner surface  16 A of the second end  16 , an adjacent portion of the upper surface  12 A of the base, an inner surface of the second wall  36 , and a part of the surface  22 B of the first side  22 . Also shown, on an opposing side of the base  12  is an inner surface of the second wall  56  of the second assembly, an adjacent part of the inner surface of the side  42 , and a portion of the inner surface of the panel  46 . 
         [0030]    Each assembly  18  and  20  is pivotally movable relative to the base  12  by means of hydraulic cylinders  80 ,  82  which act between the base and the assemblies  18  and  20  respectively. The end  16  has elongate rims  84  which extend along its vertical edges. The walls  36  and  56  respectively have corresponding U-shaped channels  84 A and  84 B which engage in a sealing, weatherproof manner with the rims when the walls are moved to the orientation shown in  FIG. 10 . Additionally a strong physical lock is formed by the interengaged channel which securely fixes the walls  36 ,  56  to the end  16 . On the other hand when the walls are moved to the compact configuration i.e. as each wall is moved to a position which is adjacent and closely spaced from the end  16 , use is made of lock bolts  86 . Each bolt includes a shank  88  and a head  90  designed to engage with a correspondingly elongate slot  94  in the end  16  when the wall is moved to the storage configuration. The interlocking arrangement is such that a strong and inherently rigid structure is achieved when the assemblies are put into the compact configurations. Cylinders  95  mounted in hollows in the walls  34 ,  36  (similarly for the second assembly  20 ) are used to elevate the second side  24 . The extremities of the foldout portion of each assembly which are to be brought into ground contact can be fitted with pistons and cylinders or other levelling devices to ensure that each floor forming component is horizontal and each wall forming component is vertical. 
         [0031]      FIG. 11  shows how the structure can be adapted to allow an interior of the structure to be accessed when the structure is in the storage configuration shown in  FIG. 1  while, at the same time, facilitating the provision of a door and windows which are usable in a conventional manner when the structure is in the operative configuration. The end  14  is formed with a rigid door  100 . The first wall  34  has an elongate window  102  and the first wall  52  has an elongate window  104 . In  FIG. 11  the structure is in an operative configuration and access to an interior is provided through the doorway formed when the door  100  is opened. The windows  102  and  104  can be top-hung or sliding according to requirement. When the structure is converted to the storage configuration the windows  102  and  104  are positioned in register with each other and with the door. It is then possible by opening the door to access the windows and if these windows have a suitable hinged or sliding arrangement it is possible to go into an interior of the structure. 
         [0032]      FIG. 11  also illustrates another variation wherein the gap  70  (see  FIG. 7 ) is closed by fabric  120 , much in the nature of a tent. This is in place of the rigid roof structure shown in  FIG. 9 .

Summary:
A structure which includes a rectangular base and two substantially U-shaped assemblies pivotally fixed to respective opposed longitudinal edges of the base, the assemblies being movable, relative to the base, into a compact configuration which is substantially of the shape and size of a conventional shipping container, and away from each other to an operative configuration at which the assemblies form walls and at least part of a roof of the structure.