or other suitable fastening means are utilized to secure the horizontal mullion to the shear block typically vertical mullion 12 is positioned and secured with the shear blocks 20 in their respective positions the installers then insert a horizontal mullion 10 over each of the shear blocks 20 and secure it with a threaded fastener 24 the installers would then move to the location for the next adjacent vertical mullion 12 a and position it in place and secure the opposing end 13 of the horizontal mullion 10 to a respective shear block 20 a mounted on that adjacent vertical mullion 12 a the opposing end 13 of the horizontal mullion 10 would then be secured to the respective shear block 20 a depending upon the size of the curtain wall there may be a plurality of horizontal mullions 10 positioned between adjacent vertical mullions 12 and there may be a plurality of vertical mullions 12 spanning the distance for the curtain wall if the horizontal mullion 10 is of a short enough span no undo sheer force occurs where the first end 11 of a horizontal mullion 10 is secured to shear block 20 however if the horizontal mullion 10 is of a sufficient span sufficient shear force is exerted on the shear block 20 prior to the second end 13 of.