Use this to fit a 3.5" hard drive into a half-height (5.25" optical drive) bay. I used dimensions from the following two standards:
3.5" disk drive:
5.25" optical drive
You can print either a full sled with a base plate, or just rails for the sides. If you use this, please feedback. Sorry about the messy code.
Print out. Place 3.5" hard drive. Use 3.5 mm or #6 hard drive screws to affix to sled.
The file is heavily commented, and comments like //A1 and //A14 refer to the dimensions given by the SFF-8301 and SFF-8851 standards mentioned in the top comment.
Some variables of note include: