Tweezers or pincers held in the hand enable an operator to take hold of a small object between the tips. The legs of the tweezers are generally flexible and transmit, to the tips gripping the object, part of the compression force applied by the hand to the legs of the tweezers. In general, the tips are apart in the rest position, except in the case of negative-action tweezers, whose legs are crossed and whose tips open under the action of compression of the legs by the hand.
It is frequently desirable for the gripped object to remain held between the tips of the tweezers without the operator having to exert pressure on the legs. This can currently be achieved only by negative-action tweezers and tweezers equipped with a rubber or leather closing ring. Movement of this ring over the outside of the tweezers, which is generally conical in shape, makes it possible to close the tips or allow them to take up their usual position, i.e. open or closed, according to the pressure applied by the hand; the operator uses his other hand to move this leather or rubber ring.