there are quilter's t-squares. and l-shape rulers...the difference between them and the hardware store ones is the thickness. the quilters are generally either 1/4" thick (or even 3/8" the hardware store ones are generally 1/8" thick. the ones from the quilt shop is acrylic, the hardware stores are steel...using metal ones (can possibly) leave marks on the fabric...which will probably wash out...you have to be VERY careful if using it for cutting not just marking because it is a lot thinner edge you are running your blade along. price -- the quilt shop ones are LOTS more expensive...but depending on the use may be well worth it