I think In-ho is the one who's actually bad at handiwork but tries to do the stuff nonetheless because he's embarrassed that he's bad at it and afraid Gi-hun would be making fun of him (Gi-hun is the real master when it comes to handiwork)
So he tries to build some new furniture for the motel alone only to end up getting hurt in the process and feels even more embarrassed to admit to Gi-hun that he hurt himself because he's bad at it.
Oh I will always have a soft spot for pathetic and helpless In-ho (I love him). And yeah Gi-hun is brilliant when it comes to handiworks, though I think In-ho knows Gi-hun wouldn’t make fun of him for being bad at it, that’s not the type of person Gi-hun is. I do think In-ho would still definitely pretend to be good at it anyway, but only because of pride.
Which is the complete opposite from Gi-hun, because unlike In-ho, Gi-hun never cares about pride. So at first he takes In-ho’s word for it (although he probably shouldn’t still believe shit In-ho says after everything but, you know, it’s Gi-hun being Gi-hun), if In-ho says he knows what he’s doing and that he doesn’t need Gi-hun’s help, then surely that must be true.
Until Gi-hun returns to the room to In-ho with his wounded hand (and pride). And when Gi-hun realizes In-ho actually sucks at it, he’s just “why didn’t you just tell me? This was preventable”. But he’s super gentle when he tends to In-ho’s wound. And In-ho just looks at Gi-hun with those 🥺 puppy dog slash boba eyes of his.