Step 1: The Materials
2 - eye-bolts (I used 5/16" x 4")
2 - 1" x 6' locking tie-downs. I picked up these ones at my local Harbor Freight for $7.99. They are plenty strong and have worked well.
2 - 5' lengths of nylon rope. I was surprised i needed this much for each handle, but it's a nice length. Make sure the cord or rope is rated to hold your weight. This can be purchased by the foot at home improvement stores or good outdoor stores. (REI, etc.)
2 - Handles. I sacrificed an old resistance band. PVC would probably work, but make sure the edges are rounded so they don't cut the cord.
Step 2: Assemble and Hang the Straps
Run the rope through the handles/pipe and tie a knot with a loop, trying to keep the same length for each handle.
Hook the straps on to the eye bolts. Keeping the latch at the top allows you to keep the excess tie-down out of the way.
Hang the handles on the other end and you're ready to go.
Step 3: Adjust the Lengths and Start Working Out.
I put the handles all the way up for pull ups, all the way down for push ups (which work your core as well), and varying heights for rows and chest flys. You can find numerous work outs online.