I cut them to the right sizes but when I nailed em 2gether they didnt line.Can someone tell me what I did wrong?

Not with the information you gave. How did you cut it? What didn't line up? Come on, if we're going to help, we need more info…

Ok,I drew out on the board what I wanted to cut out.When I cut out the parts they were fine.So I then got my nails and started nailing the bottom and left side to gether.I nailed em and they looked fine.I nailed the left side in and it also looked fine.But after I nailed the top on it was slanted and I cant figure out what happend.The sides never shifted.So some help would be greatly appriciated.Oh and I have never made a prop in my life so it may have something to do with that.

You used nails.. that is what was wrong. You probably didn't compensate for the thinkness of the wood you were useing, and probably put it together wrong with like a side sitting on a base, but not on the other.

Your right about me using nails,but I didnt have the side sitting on the base.I set off the base with the base on the inside of the sides.Im doing another and this time my brother in law is gonna help put it together.