the trailer 10 is in the vertical position shown in fig3 similarly as the trailer 10 is pivoted from the vertical to the horizontal position the assembly 16 and the wheel 17 are pivoted on the shaft 31 by pendular action until the freeend 33 engages the support 42 the supporting end 41 of the support 18 thenmoves forward on top of the arm 30 to hold the free end 33 from free rotational displacement about the shaft 31 the force for this action is obtained from the pushrod 46 which is displaced rearwardly by a combination of a gravitational force and a returning force developed by a spring 49 the action of restoring the trailer 10 to its operating configuration is now complete and further pivoting of the trailer about the supports 23 transfers the weight of the trailer 10 onto the wheels 17 the assemblies 16 the arms 30 and the suspension supports 18 a stepwise increase in cross section of the pushrod 46 near its rearward most end 48 provides a locking facility to prevent accidental actuation ofthe pushrod 46 when the trailer 10 is in the horizontal position the locking action is achieved by the stepwise decrease in cross section of the rearward most end 48.