9-1/2 minute video on drawing a pentagon with a given side length and no protractor.
The above video describes the process of drawing a pentagon with a given side length, without the aid of a protractor.
This method requires several attempts at estimating divisions of an arc. The process enables you to become more accurate after each attempt, until you have a satisfactory division.
The concept is precise, though execution is often not perfect because of several factors. The first is that pencils and compasses need to be sharp and capable of fine lines. The second is that small inaccuracies in alignment and compass adjustments accumulate into larger errors; this is called cumulative error.
The tools used are:
straight edge pencil compass
