You can use a spade handle or a right angle like the hole hog with a bullseye level mounted on the drill. With a leveled timber and the plumb drill you should have no problem roughing out your mortices. Always remember, plumb is plumb and level is always level. Gravity will never change (that goes into another topic)... But all that said if you plan on doing multiple frames, the chain mortiser will pay for itself with efficiency and accuracy.
Will Denton
