Abstract: A shock absorber for attenuating a shock effect between a fixed point and a movable element which comprises a casing, a threaded element mounted for axial movement within the casing, and a first engagement member and a second engagement member mounted for axial movement within the casing in response to a shock effect, the engagement member being in normal first contact engagement with the threads of the threaded element for converting the axial movement of the first engagement member into a rotary movement of the threaded element and the second engagement member being adapted to engage the threads of the threaded element, whereby upon the application of the shocking effect above a predetermined amount, the first engagement member becomes disengaged from the threads of the threaded element and the second engagement member abuts against the threads of the threaded element to block further rotational movement of the threaded element by becoming lockingly engaged with the threads of the threaded element while the