In a mobile telephone/PDA holder (mechanism) having a hollow body with clamping jaws supported therein by guide legs which are disposed in the hollow body so as to be slidable in unison toward, and away from, one another under control of an operating mechanism including a coupling wheel rotatably supported in the hollow body and being coupled to the guide legs, and locking elements biased into engagement with the locking wheel, the locking wheel is provided with a circumferential layer of a resilient material and the locking elements are disposed adjacent the locking wheel and have saw-tooth like projection firmly engaging the resilient material layer and the locking wheel for preventing rotation thereof in one direction but permitting its rotation in the opposite direction and a release key connected to the locking element and extending from the hollow body for releasing the locking wheel.