We present ForceStamps, fiducial markers for supporting rapid prototyping of physical control interfaces on pressure-sensitive touch surfaces. We investigate marker design options for supporting various physical controls, with focusing on creating dedicated footprints and maintaining the structural stability. ForceStamps can be persistently tracked on surfaces along with the force information and other attributes. Designers without knowledge of electronics can rapidly prototype physical controls by attaching mechanisms to ForceStamps, while manipulating the haptic feedback with buffer materials. The created control widgets can be spatially configured on the touch surface to make an interface layout. We showcase a variety of example controls created with ForceStamps. In addition, we report on our analysis of a two-day musical instrument design workshop to explore the affordances of ForceStamps for making novel instruments with diverse interaction designs.