Am often amazed at some of the simple techniques for repair of hand tools that seem to be ‘unknown’ or ‘forgotten’. 

2 of the simplest —  still common 60 years ago whem pop taught them to me as a little kid.

a. Your framing square falls off the sawhorse, and is no longer prefectly square – fix: find a good straight edge, draw the right angle lines witht he leg in opposite directions, see how far off the leg is from square. Place on anvil, peen the inner or outer corner as needed to pull/push the square back into square.

b.  You let a novice try your hand saw, and it gets a kink/bend.  Lay it on anvil, lightly peen the concave side to bring it back straight. 

c.  etc…….