Step 1: Gather Materials
First, do some homework. If you're into engineering like me, you should be able to estimate pretty well what kind of loads you'll be putting on these hooks and design accordingly. If you're not, or if you just like to play with online calculators, use this to see what you'll need for hook ratings (it's interesting to note that depending on how the hammock is hung, a 200 lb person can put over 1000 lbs of tension on the lines! Wow!) I found that lag hooks rated at 250 lbs would be sufficient for me.
2 lag hooks (you could also use eye-bolts, but you'll need something like a load-bearing carabiner to fasten the hammock to these)
2 pieces of 2x4 (or something similar) around 2 feet long
some 3.5" (or more) drywall screws
a snack (optional)
wood finish of your choice (also optional)
Probably also a hammock, and some tools. Something with which to cut your lumber, drive the screws into the wall, and drill pilot holes for your lag hooks (bonus points if you do it all with the same tool!)
Step 2: Prepare Lumber
Start by cutting the 2x4s down to size. Around 20" sounds good...
Then drill pilot holes for the lag hooks. Some of you might want to measure and make them perfectly centered, but I just eye-balled them. Don't drill them too big, or the threads won't grab. I used a bit just slightly smaller than the shaft of the hooks. You should do the same. I also did mine at an angle to be more co-linear with the force exerted by the hammock, and so that I could get more of the threads in contact with the wood.
Step 3: (optional) Dress Up the Lumber
Step 4: (also Optional) Wait for Stuff to Dry
Step 5: Insert Lag Hooks, Install Hangers
So, do you have all that figured out? Got a good spot for your hangers? Good! Screw your lag hooks into the hangers, making sure they don't stick all the way through the wood. Large pliers may be helpful here. Once everything looks good you're ready to screw in the hangers! I used about 6 or 7 screws per hanger, positioned up high so that the screws go into the top plate, or if you prefer, screw them into the studs. If you tap on your wall with a hammer you can feel where this is, or you can use a stud finder. Don't go overboard with the screws, too many will start to split and weaken the wood. Stagger them slightly if you can, rather than going in a row.
Step 6: Hang It Up!
I realize this was kind of a quick and dirty project, and there are other ways of hanging your hammock indoors, but I wanted to share what I came up with. I didn't really want to get into suspension and hanging details, those are covered in my other hammock instructable and discussed ad nauseum at the Hammock Forums.I hope it helps! Thanks, and don't forget to share your thoughts in the comments below!
Also, thanks to the mass of people who helped get this thing featured! That's really cool, thanks guys! I'm glad you like it. Again, don't forget to vote for the laser challenge!