Don't know what kinda construction you do, but I always had a box cutter/Stanley type knife in my belt. More in my pockets, but I'd just as soon cut shingles or drywall or insulation batting, whatever with a knife that's razor sharp all the time, and if it's not flip or replace the blade. Plus they take hook blades for shingles and carpet. If he's yer buddy well and good, otherwise just get him a retractable working knife for $5-10 bucks, and let him buy the 50 or 100 pack blades. Really. There's a ton of different types, folding etc., lot of them have utility notches so you don't have to expose the whole blade and are great for stripping wire, cuttin' cord , whatever. Do him and your self a favor, get him a tool he'll use the hell out of and doesn't have to sharpen. 'Cause if he ain't got a knife now,working in the trades, he's gonna have problems taking care of one in the future. Sorry if that's a rant, but I never could stand loaning my tools out , because someone couldn't make a trip to the truck or the hardware store. That stuff just don't fly. Wow, fastest I've typed in awhile. $.02
Thanks, Neal