Drawing a Circle without a Compass or Protractor

Date: 3/23/96 at 21:2:33
From: Anonymous
Subject: circles

My teacher has asked us to find out how to draw a circle without 
using either a compass or a protractor.  How do I do this?  I am 
in 6th grade.

Date: 3/28/96 at 23:12:55
From: Doctor Steven
Subject: Re: circles

Here's how I draw a circle when I don't have a compass or 
protractor. 

Basically the idea is to use your hand as a compass.  Your 
thumbnail is the pointy part of the compass and the end of the 
pencil is (you guessed it) the end of the pencil part on a 
compass.

Pick up the pencil as if it were dirty, picking it up between your 
index finger and your thumb. 

Put your thumbnail down on the paper.  Now angle the pencil so the 
lead touches the paper.

Now rotate the paper keeping your thumb stationary (and so the 
pencil is stationary also).  If you go all the way round, the lead 
of the pencil should trace out a circle.

This circle isn't so exact, but close enough for all practical 
purposes.

Enjoy.

-Doctor Steven,  The Math Forum