A manual orthopaedic surgical instrument intended to be placed on the surface of a defective glenoid fossa to measure the angle (slope) of its bone defect for selection of an appropriately-sized glenoid reamer and/or prosthesis (not included) prior to glenoid repair/replacement. It is intended to be locked into a holder (not included) and has two arms of different lengths for angle measurement; it is available in various arm lengths. This is a reusable device.