First draw the top one, it is not difficult to find, this is symmetrical, divided from the center, we only draw the left part. First draw a circle (command c), and then offset (o), select the inner circle, point "drawing" - "point" - "fixed number of equal parts", divided into eight, connected by a straight line, delete the Inner circle. The next step is the same operation, the outer circle is divided into 16 parts. Then select all of them and rotate them by 22.5 degrees. Delete the outer circle. The middle part of the rectangle and straight line are very easy to complete, we will not explain in detail. Drawing is complete, select all, point mirror, the first one is complete.
The one in the middle is a side view of the first one, so than the first one is drawn down, using a straight line to extend the above figure just about every corner down, also only half of the drawing. Obviously this is the same length, and the projected length of each part is the same, straight line, cut, OK!