A device for interlocking two sections such as a forearm-hand brace and a elbow-forearm medical device comprising, a circular strip of loop pile or hook fastener material attached to the outer surface of a first cylindrical section such as the custom forearm-hand brace. A sheet of thermo-formable material formed into a second cylindrical section matching the outer surface of the first cylindrical section wherein the second section includes a groove such that the first cylindrical section is held by the circular fastener strip within the groove and is free to rotate in either direction. A cooperating locking strap of hook or loop pile fastener attached to the second section and aligned with the strip of loop pile or hook fastener on the first cylindrical section such that attaching the locking strap to the strip prevents the free rotation and locks the first cylindrical section to the second section.