#Tip 2 Illustrator : Custom Guidelines

Do you know that you can convert any shape into a guide? Create a base geometrical shape, arc, or a line, and then go to View > Guide > Make Guide or simply press cmd-5 for Macintosh or ctrl-5 for Windows. Voila, your shape is converted into a guide now. You can use them as a stencil-like drawing guide that helps you to draw precise objects, angles, arcs, or lines. I personally use this trick to create a grid system to make a custom icon.