MARSHALLTOWN Line Blocks make it easy to maintain a straight when laying brick and blocks for any masonry project. Our Line Blocks are available in two styles: smooth poplar hardwood or a highly visible and waterproof Plastic Line Block. This Masonry tool is also in our contractor-grade QLT brand. QLT Corner Line Blocks are made of cast aluminum and are ideal for creating sharp corners. No. 16506: Length: 3-3/4 In., Pkg Qty: 2, Package Type: Bag