Abstract: An upper part 30 of a column 28 can be raised and lowered by ram 11 which is normally carried by a counterbalance unit but which can be attached to the column. The rams 11 are mounted on a chassis 10 of the unit by disengageable pivotal mounts 22/23 and are normally carried in a storage position (FIG. 2). To mount the rams on the column, they are first swung about the pivotal mounts, and are then extended to bring bosses 19 into engagement with gussets 32 on the upper column part 30. Thereafter, the rams are retracted to lift them out of their pivotal mounts 22/23, and are swung about the bosses 19 to bring them into engagement with further gussets 31 on a base part 29 of the column.

Abstract: A column is attached at a base flange to a plate of a base member by way of an offset horizontal pivot, and can be pivotally raised and lowered by means of a ram. The pivot lies in the general plane of the flange and the plate so that, when the column is fully lowered, the overall height of the unit in the region of the base member is little more than the length of the flange.