the main portion of the horizontal spacer 30 fits within the peripheral edges of the top of the 90 degree glass block 44 referring to fig7 a perspective view of the horizontal spacer 46 for a 45 degree glass block such as the tridron u00ae 45 degree block units by pittsburgh corning company is shown referring to fig8 a perspective view of main piece 52 b of the horizontal spacer 46 for a 45 degree block referring to fig7 and 8 two identical main pieces 52 a and 52 b connect together to form the horizontal spacer 46 each main piece 52 a and 52 b includes elongated tabs 48 a and 48 b and receiving holes 50 a and 50 b preferably tabs 48 a and receiving holes 50 b are adjacent on one side of each of the main pieces 52 a and 52 b and tabs 48 b and receiving holes 50 a are adjacent on the opposing side of each of main pieces 52 a and 52 b the tabs 48 a and 48 b extend perpendicularly from the main pieces 52 a and 52 b such that a square connection can be made to adjacent horizontal spacers the tabs 48 a and 48 b include barbs 56 that aid in fitting.