This is a template to help you join two pieces of wood with 3/8 inch dowels. If you use the entire template, the joint will have 5 dowels and 3 screws, which will be very strong. You don't need a drill press, just a power drill and a 3/8" drill bit.
This print requires support, unless you have a heated bed and can print the large flat base without curling (otherwise the template is not very accurate). I print at Low Quality on a Makerbot Replicator 2, with 30% infill density, for stiffness.
To use the part, clamp the pieces you want to join together, and then clamp the template on top (you could try to drill the pieces separately, but I think doing both at once works better).
Now drill all the way through the top piece and down into the second. You will need to figure out the right depth and mark your 3/8" drill bit. Then take the guide off, put the dowels in the lower piece, and slide the upper piece down on the dowels.
Initially the holes in the guide will be a bit small, so you will drill out a bit of plastic. And if your drill is a bit wobbly (mine is) then the guide might deform a little bit as you are drilling. If you feel like it is too loose, crank up the infill density.
The guide also has three 1/8" holes, for drilling screw pilot holes. You can also use these holes to re-position the guide if you need to, just stick a 1/8" bit in each hole and slide the guide down them.
I used glue on the dowels and between the pieces. If you wanted to be able to disassemble, the screws are probably enough to hold it together. If you skip the screws, you can plug the holes and the result will look relatively seamless.
For a variation on this part, see my 4-hole template:http://www.thingiverse.com/thing:673570