http://www.McCallsQuilting.com/BBW - Mary Karr-Petras demonstrates how to make a Four X Variation quilt block, including how to use the optional quarter-square triangle ruler. This Block Builders Workshop quilt block is patterned in McCall's Quilting November/December 2016. Click link above for our entire library of FREE Block Builders Workshop videos. Purchase magazine with quilt block pattern at: http://tinyurl.com/hoxc9j2