sand jack

plural sand jacks

1. businessA type of jack from which sand can be released gradually in small quantities when lowering something into position.

   1 more example

   After being rolled into position, the span had to be lowered about 4 in. on to its bearings. This was accomplished by means of sand-jacks—a simple arrangement of piston and cylinder—by which movements to very fine limits are obtained by the controlled release of sand from an opening in the base of the cylinder.

   1950 October, “Completion of Flood-Damage Repairs, East Coast Main Line”, in Railway Magazine, page 708