Used to cap masonry blocks in preparation for compression testing. The fixture consists of a heavy duty base precision ground to a tolerance of .002 in (.05 mm) in 6 in (15.2 cm) and an adjustable retainer for 4 in (10.2 cm), 6 in (15.2 cm), 8 in (20.3 cm), 10 in (25.4 cm) and 12 in (30.5 cm) masonry blocks.