In my assembly file the holes and screws for the hinges keep moving. The holes are fully constrained so I don't know why they move.
They moved because your holes are an assembly feature made on parts that move. If you were to propagate the hole features to the parts and then break their dependency on the assembly they will work for you just fine.
My advice is to make the screw holes in the hinge parts first. Think about it, if you were to buy the hinge wouldn't it already have the holes in it? In the assembly make the holes in the other components to match these hinge holes and then break the relationship so the hole features are completely independent of anything outside the part file. These holes fall into the category of Top-Down assembly. That is fine, but not for a newbie and especially not for a moving set of parts such as your door and hinge.
Here they would say "Problem In Denmark"
I put the holes in the assembly so the holes in the hinges and the holes in the mailbox would line up. Is there another way to do this?
1. If you do an assembly feature of the holes make sure to "propagate the feature to the parts". Read up on this in the Help file.
2. Alternatively (and this would be my preference), with the holes already in the hinge pieces, Edit the lid and the bottom (separately) in the context of the assembly. Add the holes to those parts by referencing the holes in the hinge pieces. My advice is to then break these in-context relationships and lock down those hole locations with dimensions.
I couldn't find it on the help section, but is this what you're talking about?
SolidWorks How To Transfer Hole Location to Different Part in Assembly - YouTube
I can't get the circle with the plus to appear.
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