Abstract: A Ceiling Joist Clamp (used in pairs for most effectiveness) which can be fitted securely to a ceiling joist or to metal-frame stud to provide a unique supporting ledge that sheet material i.e. Plasterboard can slot onto thus being supported on one side whilst being fixed to the ceiling joist. The support ledge is unique because of its curved profile, bending downwards in a sweeping or radius bend and extending vertically to provide a vital secondary support area to facilitate the lifting of the sheet material up to the ceiling and into the support ledge.