An assembly is provided for operatively connecting a first object which is capable of a to and fro movement, with a second object, in such a manner that the second object, when connected to the first object, will move in correspondence with the first object. The first and second objects are provided with first and second facing ends, respectively, provided with cooperating first and second coupling provisions, respectively, wherein at least one of said objects is housed in a guide. The coupling provision of at least one of said facing ends is capable of cooperation with said guide for moving said coupling provision from a first position disengaging the other coupling provision to a second position engaging the other coupling provision in which both objects are connected.