A number of techniques may be employed to control the figure of a bent mirror. The accuracy of profile obtained depends on the accuracy of manufacture of both the mirror and the bending block. The profile should be verified by dimensional metrology, and the adoption of 'open' designs of bending block facilitates access for metrology. Open access to the bent mirror surface also facilitates in situ inspection by other techniques, such as interferometry and microscopy. A new design of bending block provides such access. The mounting for the bending block also maintains the pole of the mirror on a fixed axis regardless of mirror curvature, and the length of mirror illuminated is constant regardless of the angle of incidence set.