Rule of ThumbPencil measurements at arm's length
This is a very simple way to assess angles and proportions when sketching. Hold a pencil at a full arm's length in front of you. Align the top of the pencil with the top of the object, then slide your thumb down the pencil till it's aligned with the bottom of the object. Keeping a firm grip on the pencil quickly lay it on the drawing paper and mark off the two points. This method can be used effectively to quickly assess and check angles on buildings objects and the human figure.