Handy Four Pack for Single Installations CRL Storm Window Clamps are a handy exterior clamp that speeds up your storm window or screen installation time. The screw-type clamp allows for up to a 3/4 inch (19.1 millimeter) adjustment. Using a slotted screwdriver, screw the clamp to the window jamb, place your sash or screen into position, swing the clamp over the frame and snug down the plastic screw. Minimum Order: 1 Pack Four clamps and screws per package.