When referring to a concrete speed block, a mason usually means a mortar-less head joint, or H-block. A speed block is rectangular concrete masonry unit (CMU), or cement block, that is constructed in an open-ended “H” configuration. These blocks differ from the standard CMU, which is usually closed-ended, and will have two or three core holes. CMU’s are manufactured in a wide variety of sizes and configurations to accommodate the various convolutions of building construction. These vagaries include window and door jambs, corner braces, columns, etc. As a rule, speed blocks are used at the top joints of a structure because of their lighter weight and more versatile configuration. The common speed block is nominally 8 inches wide (20.32 cm) by 8 inches (20.32 cm) in height by 16 inches in length (40.64 cm). Standard concrete blocks have the same dimensions, and all are actually 3/8-inch (1.02 cm) less all around to allow for a joint of mortar between blocks. The common speed block, howev