Abstract: A surgical tool, such as grasping forceps, biopsy forceps, or a retaining basket, is operated by a control wire that extends through a sheath. A handle assembly has a luer at one end through which the control wire passes before attaching to a slider that is movably located within an elongated opening in the handle. The slider has a collet mechanism that grips the wire and the luer is rotated to tighten and loosen the collet mechanism. A brake selectively applies a force between the handle and the slider to restrict movement of the slider within the elongated opening of the handle. In different embodiments, the brake is attached to either the handle or the slider and exerts frictional force on the other components. The handle assembly is designed to enable single handed operation of the surgical tool by a user.