after insertion of the pin 4 the whole is secured together by a nut 5 spacers 14 set out between the contact walls of elements 12 and 13 may optionally be incorporated with the intent of facilitating the pivoting thereof although the above embodiment features the presence of a shackle at the junction of elements 12 and 13 and in the creation of a pivot point for the same elements 12 and 13 can alternatively be initially fixed in place by a hollow shaft that traverses the upper holes of both in this case the shackle or any other equivalent connection element would traverse the interior of the hollow shaft likewise the point of pivotal fixation of element 12 in element 13 can be in a position other than the upper hole of element 13 element 12 may for example be attached to element 13 on an axis positioned on the intermediary part of the latter in this case the presence of only holes would be required in element 13 with element 12 comprising a single hole also by way of an alternative elements 12 and 13 could have an adjacent configuration where instead of an element receiving the other in its.