The film starts with Stan and Ollie dumping a load of building materials from their van; when the van starts to roll backwards suddenly the space behind it is empty.
Stan pulls a lever in the lorry cab causing the tipper back to go up discharging all the frames. After Ollie puts a rock under the back wheel there's no sign of the frames.
At the end when the lorry starts rolling down the hill towards the house there's already wheel tracks in the ground which weren't there before and were obviously from a rehearsal.
Ollie tells Stan to do some sand papering. Stan gets a sheet of sand paper which can be seen is new. Before he can use it the nurse comes in and remonstrates with them about all the noise. As she bends down to pick up a hammer Stan tears the sheet of sand paper in half but it can now be seen to be a used sheet.
Ollie steps on a pile of nails. a close up of his foot shows that a number are sticking out which is highly unlikely.
At the beginning of the film, a van is rolling downhill before being caught. As it stops a crew member is visible outside the cab on the driver's side, controlling the van.