Random Oracle Model.

A reworking tool for ceramic substrate hybrid circuits has a metal base for sitting on a heated surface, a support member support above the base and a pillar of heat conductive material attached to the base and extending up through an aperture in the support member. The top surfaces of pillar and support member are in a common plane. By this means a "hot spot" is produced at the top of the pillar and a hybrid circuit positioned on the support member can be so positioned that a particular component position is resting on the top of the pillar. Solder at this component position will melt and a component can be removed, or a component added or a component removed and another placed in position. Lateral sliding of the hybrid circuit laterally on the support member enables the solder to solidify.