How do I fix my hat problem?

My script was working perfectly then I found a problem. When I went into the actual game the hat that was placed in the player didn't get attached to the player. So how would I fix this?

It's probably because you needed to weld it.

Here's how to weld:

local weld = Instance.new("Weld",part1)
weld.Part0 = part1 -- the first part you want to weld
weld.Part1 = part2 -- what you want to weld it to

Yup, that's it!

Also, please include your code in your questions.