Four 1/2" Dowels, cut to 8" long
One 15" diameter round wood thing
Two approx 18" squares of fleece
A heating pad
Four 1" screws
A 1/2" drill bit
First drill the four holes into the base of the hammock. Each hole should be about 1.5" away from the edge of the base, and should make a square as shown. Drill in at an ANGLE of about 60 degrees, and stop when you hit the bottom.
Next go ahead and attach a screw into each dowel. The screw should stick out about a half inch , so that it can be used to mount the hammock. I place my screws about 3/4" down the dowel, but it can be moved up for larger cats or down for smaller ones, so long as each screw is about the same height on the dowel.
Next slide the dowels into the base. You can use glue if you want, but I found that mine didn't need it. Make sure that the screws face away from the base.
Cut strips about 1" wide and 2" long down each side of your fleece squares. Line them up and knot them together on three sides, pretty side out. If you're having trouble, look at these instructions.
Slip the heating pad through the remaining open side. I had to fold mine in half. Make sure the power cord is still accessible, then knot the remaining side closed. Mount the hammock by slipping one corner knot over each dowel. You may have to stretch the fleece to do this. The knot will stop sliding at the screw, so that your heated cat hammock sits suspended and comfy.
If I come back to this project later, I think I'll add a primitive pressure sensor and wire it to a relay, so that I don't have to turn on the heating pad when the cats climb in - it'll turn on all by itself. To do that, though. I would need a different heating pad, or I'd just need to rewire the controls on this one, which requires you to press a button to turn on.
Here's a picture of the wrong cat, Nicodemus, sleeping in the hammock to spite his sister.
And this is Skitty, who wouldn't climb in until I put her there, and wouldn't leave once I did. You're welcome.