Sirr0und Marshalltown Wood Line Block Model No. 86. 3-3/4" long. Preferred by many bricklayers. Used to make sure that a course of bricks is straight and true. As the line is pulled tight, the blocks hold their position by friction on the bricks. Packed 1 pair in a bag. MPN# 16506 SKU# 314986UPC# 35965065061