29 CFR 1926.305 - Jacks - lever and ratchet, screw, and hydraulic.
(2) All jacks shall have a positive stop to prevent overtravel.
(c)Blocking. When it is necessary to provide a firm foundation, the base of the jack shall be blocked or cribbed. Where there is a possibility of slippage of the metal cap of the jack, a wood block shall be placed between the cap and the load.
(1)Operation and maintenance.
(i) After the load has been raised, it shall be cribbed, blocked, or otherwise secured at once.
(iii) All jacks shall be properly lubricated at regular intervals.
(a) For constant or intermittent use at one locality, once every 6 months,
(b) For jacks sent out of shop for special work, when sent out and when returned,
(c) For a jack subjected to abnormal load or shock, immediately before and immediately thereafter.