Found these weird self-adjusting wrenches in my dad's old toolbox - what are they actually for?

Those are self-adjusting wrenches, sometimes called ratcheting or spring-adjustable box wrenches. That knurled thumb screw on the side moves the jaw in and out so it clamps the fastener instead of needing an exact size like a fixed box end. Craftsman sold a bunch of these over the years, and the red rubber grips plus the stamping sounds like something from the 80s or 90s era Sears stock. For your uses, keep them in the drawer category honestly. The design has a real weakness: the clamping jaws round off bolt heads if you pull hard on them, especially older or rusted hardware like fence fittings that are already halfway rounded. They're fine for snugging something up or breaking loose a bolt that's in decent shape, but under heavy torque the jaws can slip and chew the corners. A regular combo wrench grips all six flats and won't do that. What they're actualy good for is situations where you don't know the size or you're dealing with a few diferent sizes in a row and don't want to swap wrenches, like plumbing-adjacent stuff or odd hardware. I keep one in the truck for that exact reason. For mower work and fence hardware, your standard set of combos and a decent adjustable crescent will serve you better. The cracked rubber grips are purely cosmetic as long as the metal underneath is solid. Check for cracks in the steel near the head or handle junction, and any wiggle in the thumb screw mechanism. If the screw turns smooth and the jaw moves without binding, the tool is mechanically fine. A little oil on the screw threads and a wipe down will keep it that way. And honestly, given they were your dad's, there's no shame in the drawer anyway. Some tools earn thier spot by being useful, some by just being his.

Second the drawer thing, I found one in my grandfather's rollaway and it stays there mostly for the sentimental value. I did try it on some car battery hold-down bolts once and it worked okay because they were only finger-tight plus a quarter turn. Anything beyond light duty and I switched to a proper wrench. One thing I noticed: mine had gunk hardened in the jaw pivot, so I soaked it in penetrating oil overnight and cycled the thumb screw til it moved freely again. Might be worth doing before judging how yours feels.

My dad had a pair of those too and I ran into the same cracked grip problem. What actually brought mine back was a thick heat-shrink tubing sleeve over the handle, shrunk down with a heat gun, gives a fresh grippy surface over the old rubber. Cheap fix and it feels better than the original anyway. On the use side, mine earned its keep tightening the nuts on the toilet supply line where three different sizes showed up in the same spot under the sink, no swapping tools mid-job. That's the kind of thing they're good at, not heavy torque stuff.

Mine came from an old toolbox too and honestly the thumb screw gets sticky if you don't use them for years. I put a tiny drop of sewing machine oil on the threads and worked it back and forth for a few minutes, now it turns like new. Also worth flipping them over and using them on the far side of a bolt sometimes, changes how the jaws load and they slip less on stubborn stuff. Still grab my regular wrenches first nine times out of ten though.