the invention will be better understood from a perusal of the following description of a non - exhaustive example of the invention and in the light of the accompanying drawings , in which : fig1 depicts a view of an equipment support according to the prior art , fig2 and 3 are general views of the front and intermediate cross members , mounted between which is an equipment support according to the invention , fig4 and 5 are flat views , respectively from below and from above , of the equipment support according to the invention , fig6 is a partial view of the front end of the support according to the invention , indexed and attached to the front cross member of the roof structure , fig7 is a view from below of the front end of the support according to the invention , illustrating the region of the plate , fig8 is a partial view of the rear end of the support of the invention , illustrating the means for the pre - retention and the attachment of the support to the intermediate cross member , fig9 and 10 are views of the foot of the rear end of the support applied and attached to the intermediate cross member in the area of the central recess , fig1 is a partial view in perspective of the front end of the support of the invention , to which the roof console is attached in part . in the following description , the directions are indicated with reference to the conventional xyz benchmark for the vehicle , in which x designates the longitudinal direction of the vehicle , facing towards the rear , y designates the transverse direction of the vehicle , facing towards the right , and z designates the vertical direction . front 1 and intermediate 2 cross members of a motor vehicle according to the invention are depicted in fig2 and 3 ( the sheet metal part of the roof is not depicted ). these cross members 1 , 2 are substantially parallel to each other and extend transversely to the longitudinal direction x of the motor vehicle for the entire width of the vehicle . the intermediate cross member 2 is located at right angles to the “ b - pillar ” of the vehicle , conventionally corresponding to the rear pillar of the front door frame . the cross members are structural elements made of pressed steel having a substantially trough - shaped or u - shaped cross section , of which the concave part is oriented towards the top and of which the edges are welded to the sheet metal roof panel of the vehicle . a support 3 for multifunctional pieces of equipment is mounted between the front 1 and rear 3 cross members . this support 3 connects these cross members 1 , 2 together substantially in the middle thereof . the support 3 is typically made of an injection molded plastic material . as illustrated in fig4 and 5 , the support 3 has a generally elongated form extending in the longitudinal direction x . it includes , from its front end 4 as far as its rear end 5 : a plate 6 forming an enlarged zone , located on which are a plurality of clip - fastening structures , a central structural beam 7 connecting the plate 6 to the intermediate cross member 2 , said beam being provided in particular with one or more clips and / or with clip - fastening structures for cables distributed along the beam 7 , a foot 8 for attaching the beam 7 to the intermediate cross member 2 . with reference to fig4 to 7 , the support 3 includes , at its front end 4 , indexing means 9 , typically constituted by two pins extending in the longitudinal direction x , each having a pointed end and a ribbed body , of which the transverse section exhibits the general form of a cross . these indexing means 9 are configured to be introduced snugly into corresponding orifices provided in the front cross member 1 . these orifices are provided in a substantially vertical rear face of the front cross member 1 . these indexing means 9 are adapted to the edges of the orifices in order to ensure positioning in the transverse y and vertical z directions . in addition , the first end 4 of the support , and more specifically a substantially rectilinear front edge of the plate 6 , interacts in a bearing manner in the direction x with the same face of the front cross member 1 , in such a way as to achieve adequate positioning of the support 3 in the direction x in relation to the front cross member 1 . as depicted in fig8 and 9 , the support 3 includes , at a rear end 5 , clip - fastening structures 10 located on the attachment foot 8 . the latter are constituted by elastically deformable feet penetrating vertically into corresponding orifices provided in the horizontal lower face of the intermediate cross member 2 . these orifices have a dimension in the longitudinal direction x which is greater than the dimension of the feet , such as to absorb any variations in production or in positioning between the front 1 cross member and the intermediate 2 cross member . typically in this case , the orifices receiving the clip - fastening structures 10 exhibit a generally elongated form in the longitudinal direction x . the intermediate cross member 2 includes a lower face provided with recess 11 at its center ( fig9 - 10 ), said recess 11 receiving the end foot 8 of the support 3 forming a deflection facing downwards relative to the beam ( 7 ). the recess 11 allows the thickness of the foot 8 to be integrated into the overall thickness of the intermediate cross member 2 , such that the headlining ( not depicted here ) may be applied and attached to the cross member without forming an excess thickness at the location of the foot 8 . the support 3 is in addition attached securely to both of the cross members ( ) by means of screws at the front 12 ( fig6 - 7 ) and at the rear 13 ( fig8 - 10 ) passing through each of the ends of the support 3 . at the front , a screw 12 is located between the indexing means 9 , for example , and is oriented parallel to the latter , said screw being screwed into the face against which the support 3 is in bearing contact . at the rear , a screw 13 is screwed vertically into the horizontal lower face against which the foot is in bearing contact and is pre - retained by the clip - fastening structures 10 . the support 3 includes clip - fastening structures 14 ( fig4 ) for cables 15 ( fig7 ) and / or for electrical connectors 16 and / or for wireless signal transceiver ( s ) 17 . these cables 15 are typically power supply cables for the rear lights , power supply cables for the air conditioning system and / or multimedia cables ( navigation , radio ). the wireless signal transceiver ( s ) 17 are connected , for example , to the navigation system . they may include a receiving antenna for a hands - free access system ( for example with a card or a badge ) or some other antenna or transceiver . these examples are provided purely for illustrative purposes and are in no way exhaustive . the support 3 thus comprises a set of forms or housings that are complementary to the aforementioned cables and pieces of equipment and enable the latter to be retained by clipping . it should be noted that the support may also receive clips by clipping , said clips themselves being provided with complementary clamps or clipping means for the purpose of retaining the cables in particular zones . for example , two clips 18 are positioned along the beam 7 of the support 3 enabling a cable 15 to be held running along this beam 7 between the front cross member 1 and the rear cross member 2 . the beam advantageously includes orifices 19 ( fig9 ) providing access to a concealed part of these clips 18 , with the help of an appropriate tool such as a screwdriver , enabling these clips to be removed without being obliged to remove the support 3 in its entirety or running the risk of breaking an element . numerous clip - fastening structures 14 are located and concentrated on the plate 6 in front of the support 3 , thereby constituting a technical zone having an abundance of various pieces of equipment , permitting easy repairs or desired upgrades . the support 3 further includes clip - fastening structures 21 for a central roof console 20 ( fig3 , 11 ) incorporating operating controls and / or visual displays . these clip - fastening structures 21 are downwardly projecting , for example , or receive corresponding clipping feet formed on the roof console 20 . in the illustrated case , the roof console 20 is attached in part to the plate 6 of the support 3 via appropriate clip - fastening structures , and in part to the front cross member 1 ( fig1 ). the support 3 according to the invention made of a plastic material advantageously comprises stiffening ribs distributed over its entire surface and in particular in the zone of the beam 7 , thereby making it possible to guarantee adequate mechanical strength . such a roof structure comprising such a support 3 allows a large number of cables to be passed into the central zone of the roof , which does not overfill the lateral zones of the roof where other pieces of equipment are present , in particular inflatable bags or airbags ®. the support 3 of the invention is light , robust , multifunctional ( support for various pieces of equipment ), non - aggressive and easy to install at the time of its assembly on the vehicle . the assembly ergonomics is improved in particular with respect to the indexation and the pre - retention on the cross members . the invention is not , of course , restricted to the embodiments or variant embodiments described above and includes all the technical equivalents of these means .