Abstract: Clamping or expanding pliers having a first plier arm pivotally connected to a second plier arm, and a toothed structure attached to the first plier arm. A catch member is movably connected to the second plier arm. A single bias spring biases the plier arm apart and biases the catch member to a resting position engaged with the toothed structure. Either with or without the single bias spring the catch member may include an intermediate release position allowing a separating movement of the first and second plier arms without disengaging the catch member from the toothed structure. The first and second plier arms may include a resiliently deformable plastic, with the catch member arranged so that the force required to move it to its release position is lower than the clamping force.