Abstract: A wrench for installing or removing filter cartridges in locations of limited access, consists of a pair of joined sheet metal stampings having cartridge engaging flanges thereon, arranged to be drawn together by a cam and slot mechanism, operated by an axially applied tool. The stampings are slidably pinned together for limited relative movement. One of the stampings supports the cam for revolution while the other stamping includes a transverse slot in which the cam is disposed to effect the relative movement. The cam and slot are arranged so that inward clamping movement and thus gripping of the cartridge occurs upon revolution of the cam in either direction.