Sally Jupiter Costume (Silk Spectre I) from Watchmen

Step 15 Garter Panties / Suspender Briefs!

Step is Very much Optional.  You can buy your own bodysuit with attached garters or garters/suspenders to use.  I could not find any I liked, and could not find garters/suspenders with the Y-shape seen on hers, so I wore a black overbust corset to act as the bodysuit she wears, and I made my own garters for a pair of panties I purchased that looked somewhat similar to the pattern of the bodysuit she wears in the movie.

I measured the length from the bottom of the briefs to the top of my thight highs and added a seam allowance for overlapping, and cut pieces of garter/bra elastic to those lengths.  I cut 4 more pieces.  One pieces each to do with each of the other four, each of these pieces shorter than the originals, so that they would create a Y-shape when places at the proper angle and stitched together.  
I put the tops of the elastic pieces through my hooks and the bottoms to my metal garters. 

I then took pieces of the lacing I had left over from the belt, neck, and wristlet, and used it to make loops to attach to the briefs (to hook the garter straps to the briefs).