2 ways that I've seen done that work well:

1) block the inside of the guitar, , insert the reatiner clip, and tap it
with a mallet on the end of a sawed off broom handle to straqighten
it up.

2) a better solution! -- get a stack of 6-8 washers that just clear the
inside of the hole in the body, , get a bolt that will fit thru the hole
(smaller than 3/8" diameter of course, and put the bent clip in, and
put half hte washers on each side, insert the bolt thru, and tighten it
up... works the same as the tool that stew-mac sells.