A hand sander for finishing both planar and arcuate surfaces is disclosed which provides a means whereby the flexible abrasive strip is shifted relative to a backup member so that it remains taut irrespective of whether a planar surface, a concave surface or a convex surface is being finished. The base or backup member comprises an elongated flexible strip having hand grips mounted thereon. Loosely coupled to the backup member is a further strip of flexible material having means for clamping opposed ends of the abrasive strip. First and second pairs of cooperating wedges are affixed to the base member and the clamping strip so as to cooperate with one another so as to effect the degree of displacement between the base and clamping member as the base member is passed over an arcuate surface to be finished.