Alvin Professional Parallel Glider

"An easy-to-use instrument that combines the functions of a parallel straightedge, triangle, protractor, T-square, and compass in one. One of the most useful and convenient aids for drafting, drawing, and nautical applications. Smooth gliding action to easily make parallel lines without twisting or turning under accidental pressure. Features durable acrylic blade with printed graduations, through-holes at ½" increments for drawing circles, and a comfortable aluminum roller bar with non-skid rubber O-rings for a firm grip on any surface. Individually blister-carded with detailed instructions included."