Abstract: Apparatus applicable to the piston rod of a control cylinder inherently operable to selectively limit and control the extent of its retraction. A preferred illustrative embodiment, as applied in use, conforms to a generally L-shaped structure the long leg of which is slim, substantially uniform in width, at least in part transversely arcuate along the length of its inner operative surface, highly resistant to compression and has its base end pivotally connected to the short leg of said structure. Springs interposed between these legs in the pivotal interconnection thereof are established in a secure and stable relation thereto in a manner to positively apply in continuing bias on the long leg which induces it to incline to and over the length of the short leg to inherently form therewith an acute angle. These legs are so formed to lend the minimal amount of material of which they are comprised a very high degree of load bearing strength for their size.