Just the other day I noticed I had a massive amount of cross-bolts and nothing to do with them so i decided to make a crossbow substitute, the Sling-bow! In this instructable, I'l be showing you how to mod your slingshot to shoot cross-bolts ( or arrows) AND rocks. Don't worry, you're not changing the slingshot, just adding to it so you can always remove my mod and revert back to normal.
First, you'l need:
*1 Slingshot ( I used a Powerline P51, you can check if your slingshot will work by checking for the two screws mentioned in step1)
*Some Scrap metal you can cut to your dimensions ( a 6 in by 1 in rectangle will be fine)
*A heavy hinge lock
*paracord or suede cord
*A bolt and nut
*and some tools such as a screwdriver, drill, tin snips, grinder, etc.

Step 1: Preparing the Slingshot

First, remove the screw nearest to the slingshot's fork. This screw will hold on your guide for cross-bolts. Then, using whatever method you please( I prefer a bench grinder), grind a little half moon out of the bottom half of the heavy duty hinge. my modified hinge is on the right. as you can see, it's not a very big half-moon, just big enough to accommodate the the rear screw on the slingshot.

Step 2: Adding the Metal

Now, it's time to cut some metal! First, pull the slingshot bands straight back as if you were shooting the cross-bolt out of it. The height of the metal guide for the bolt should make the bolt lay perfectly level, just as it would in a crossbow. If it helps any, my piece of metal between the forks is 2 3/4 inches high. After that is cut, cut another piece of metal which will lay over the hinge acting as a safety support. The size of this piece should be as wide as the hinge. Now drill one hole at about 1/2 in on the bolt support( piece between the forks) and just in the center on the safety support. Now assemble the main mod like the picture, just screw the Bolt Support to the small end of the hinge.

Step 3: Adding the Hinge

Now, place the hinge on the sling shot frame. It is important the the hinge is connected exactly as the picture on how it gets taller as it runs down the sling shot body. Now put your last piece of metal, the Safety Support, over top the initial screw hole and run the old screw back in. Be sure to do this tightly, you don't want this popping off!

Step 4: Finished!

Finally, if wanted, you can run a piece of paracord or suede cord through the holes in the pouch where the rubber bands are tied. Doing this will simulate a crossbow more and make it much easier to grip the cross-bolt. Now go out and hoot your Sling-bow!

Safety Warning- This Sling-bow is dangerous! Never shoot this as another person and always wear safety glass during operation and while around the operator!