If you want to start 2D Mechanical Design with AutoCAD this is a very good help to understand the most common commands. This booklet shows you how to use the commands: Line; Xline; DIM; Offset; Trim; Layer; ZOOM; Copy; Wblock; Insert; Dimstyle; Hatch; Osnap; Circle; Mirror; Explore; Lengthen; DDattdef; Dtext; Erase; Fillet; Chamfer.