Continuity mistake: When Stan is using the smoothing plane on the piece of wood, a pot of glue is next to the bag on the table, but when Oliver leans over the table in the next shot, it is next to the saw.
Continuity mistake: When both Stan and Oliver walk into a plank that's being carried, in the background there is a jumbled pile of timber. But in a close-up of Stan and Oliver sitting on the ground, it is now a tidy pile.
Continuity mistake: When Oliver has his hands trapped in the window frame, Stan looks at the blueprint of the Boulder Dam and the strap on Oliver's overalls is up. In the next shot, the strap is down, and in the shot after that, the strap is up again.
Continuity mistake: When Oliver gets stuck in the vent port, he has his arms tucked inside. When we see Stan climbing up a ladder to give him his bowler hat, Oliver has his arms outstretched.
Revealing mistake: In an overhead view of Oliver Hardy going down the sawdust chute, you can see it is a stunt double.
