A support (1) of a rigid material having a salient arcuate bow (6) extending orthogonally from one side of the vertex of a saddle portion (5) has a Velcro.RTM. hook part (2) fixed onto the concave surface of the saddle portion (5) and a coating of a cushioning material (3) on the convex surface of the salient arcuate bow (6). The support (1) is fixable onto a wrist band (P) by anchoring the Velcro.RTM. hook part (2) present on the concave surface of the saddle (5) onto a textile lace (9) of the wrist band (P) passed in front of the thumb, the coated convex surface of the salient arcuate bow (6) sustaining the thumb resting on it. A textile binding lace (7) is wound around the thumb and the sustaining salient arcuate bow (6) of the saddle (5) for immobilizing the thumb.