Abstract: A dial which includes a knob mounted on a rotary shaft and a dial surrounding the rotary shaft against which the knob may be positioned and including a base which rotatably supports the rotary shaft upon which the knob is mounted and clamp means between the knob and the base which comprises a brake shoe formed on a top surface of the base and in contact with a lower surface of the knob and a brake lever which has a projection such that in one position the projection engages the brake shoe to urge the brake shoe against the lower surface of the knob to lock it at a predetermined position. The brake shoe is formed with a slit in either its inner or outer flange and the brake lever is formed of a substantially similar circular shape which is rotatable within a groove and with the projection provided at one of the free ends of the brake lever.