I recently attended a Diane Loomis Heirloom Machine Quilting Workshop with the Waterloo Region Quilter's Guild and Diane suggested we use a tool called the "June Tailor Grid Marker" which came out in 2006 and I'm not sure where I was at that time because I never knew about it and it is wonderful!!!
Some may think it is like the strip cutter (also by June Tailor but it is not, a rotary blade will not fit in the line gaps, there is room for a marking pen only). It is like a stencil for line marking. I see yards of fabric marked with this grid and made into quilted bags, pot holders, placemats, quilts etc.. However, by now I cannot hide my excitement for this tool!
This tool will save time as there is no need to continuously mark with a ruler, move and mark and reduces errors.
You can use it for 45 degree squares, 60 degree diamonds, straight lines horizontally, vertically and diagonally, double lines etc etc etc. The sky is the limit depending on your own imagination using straight lines.