The present invention is an adjustable support for installing a planar sheet of material between opposed surfaces for protection from events such as storms. The supports secure the planar sheet to an opening such as a door and window, thereby holding it in place during storms, etc. The supports are easily removed and include a substantially L-shaped base and a clamp. The clamp is removably and adjustably attached to the first side of the L-shaped base, thereby forming an aperture between the second side of the L-shaped base and the bottom surface of the clamp. The aperture is adaptable to accept various thicknesses of substantially planar objects. A device is provided for engaging the adjustable support with a support structure, passing through the clamp and passing through a hole in the first side of the L-shaped base and interfacing with support surfaces to hold the substantially planar object between the first support surface and a substantially opposed second support surface.