I have a GMC truck, and I'm tired of putting it in my back seat. So, does anyone have a home made mount that they use for the bed of a truck.

http://www.performancebike.com/shop/Profile.cfm?SKU=3702&item=00-1616&slitrk=search&slisearch=true 

 I mean in the bed of my truck.  Any ideas on how to mount the bike mount in the bed of my truck, without drilling.

I would think you could cut down a sheet of plywood to fit and attach the universal mount - like the ones from Performance.  Then when you want to transport the bike lay the plywood in the bed. And when you didn't need it, you could stand it up in the garage or stow it in the rafters.

You might want to turn the plywood 90-degrees so that it's wider than the space between the wheelwells - and then cutout around the wheelwells. If you cut it correctly it will stay in place and not shift or slide. You could even mount tie-downs to the plywood to secure straps or bungees, too.

 Attach the mount (preferably 2 or 3 of them) to a 2X4.  You should be able to wedge the 2X4 in the truck so that it's secure, or you could weigh it down or attach it some other way.

 How about this?

 This is not exactly what you are looking for, but it may give you some ideas. This is how I roll in my 2000 CR-V! Sorry about the excess flash.

Just a 2x2, some quick mounts, and some mending straps. I bought the straps when I installed a new garage door opener. I cut the leftovers to length with a cut-off wheel mounted on my (corded) drill.Then I notched out one of the holes to align with the screw head. Honda was nice enough to install those screw heads on the back of the seats. Apparently they are supposed to help you stow the headrests when the seats are folded down, but it just seems like a lot of extra trouble. Even with the seat all the way back, my 61 frame clears the back door by about 3/4". I do have to remove the seatpost. Eventually I may come up with a way to secure the front wheel.

All bow to my manly ingenuity and use of power tools!

Here's what I did in my old Mazda when I was a poor college student and bike racer.

My plan works best if you have a bedliner, but may work ok without it.  It cost me less than $10.

1. Cut a 2X4 so that it fits width-wise in the bed behind the back window.

2. Get some L-shaped aluminum.  This is easy to find at hardware stores.  About 2" X 2" angle is good - enough so you can drill a hole in the center of one leg and have enough room below the hole (you'll be mounting an axle in it) so your dropouts don't hit the bottom of the L.  1/8" to 3/16" thick is about right.  Cut it in sections about 2-3 inches wide (a 2X4 is around 3-1/2", so anything close to that is fine, but the wider the more stable).

3. Find some old front axles with the cone nuts and locknuts (I don't know if those are the right names, but you need 2 nuts for each axle).

4. Drill a hole in the center of one leg of the L section so the axle will fit through but is a tight fit.

5. Put the cone nut on the axle, then put the L section on, then the locknut.  Do this for both sides of the axle.  Run a skewer through the axle.

6. Put the assembled piece on the 2X4 towards the side of the truck.  It may help to put your bike on it to get the location right.  Drill 4 holes in the bottom of the L bracket and into the 2X4.  Put good long wood screws into those holes to attach the mount to the 2X4.

Typically you can fit 2 bikes side by side.  With a big truck it might be possible to make 2 mounts and put one facing forward and one backward to fit 4 bikes.

If you have a bedliner you can remove, pull it out and flip it over and drill holes through it into the 2X4.  I put these holes in the ribs of the bedliner so that the bolts that go into it were recessed and wouldn't scratch the paint.

That's about it.  It worked great for many years.  If you really want to make it secure for longer drives, run motorcycle tie downs from the left side of the bars on the bike to the left and the right side of the bars on the bike to the right down to the tie down loops in the bed of the truck.  Then put one more tie down from one bike's bars to the other.  Cinch all of them up and it will be very secure.

I had axles and skewers laying around and Al angle as well, so the only things I bought were screws and tie downs.  You could probably get axles cheap from a bike shop since you don't need them to be nice.

Oh, to finish it all and protect it from the elements, paint the 2X4, angles, and axles with some decent spray paint.

EDIT - all that explanation and inillinois' pictures are pretty close to what I did except I made the mounts instead of buying them because I didn't have the dough at the time.
 

 I just finished the bike rack.  I will post pictures when I have time today.  I have to hurry right now b/c we are headed for the lake!  Thanks again for everyones advice.  I took a little from everybody.

Curious to see your solution...  I just took a pair of fork mounts and screwed them into a 2x6, so it'll take 2 bikes.  Fast & cheap, and it's lasted for years (probably at least 10, I don't even remember when I put it together anymore).  Easy in/out and plenty secure side-to-side although it can still slide fore/aft a little if you don't use a bungee cord or 2.

 Here are the pics.  2 2x4 $5.00, Thule bike mount $10, everything else I already had.