This paper (i) gives precise formulations of different variants of the boundary condition of clamping for shearable rods, (ii) shows that modes of clamping resembling that for unshearable rods must be maintained by artificial devices, which prevent boundary conditions from being conservative, and (iii) shows that some equilibrium problems for shearable elastic rods clamped in this way have surprising instabilities at infinitesimal loads. These instabilities are illustrated for concrete problems.