Abstract: This seat belt locking device is utilized to temporarily modify a shoulder/lap belt occupant restraint system in a vehicle to secure a child's restraint seat in place in the vehicle. The clamp has a base on which overlapping shoulder and lap belt webbings are placed on a locking bar pivoted to the base is used to force the overlapping webbing to an offset, high friction position. A camming and retaining knob is turned over the free camming end of the clamping bar to further tension the lap belt webbing and to secure the bar and the webbing offset thereby in position so that the lap belt can be effectively employed to keep the child restraint seat in position under a wide range of seat belt loads as encountered during normal driving conditions.