Last year I helped organize and prepare my Venture (scout) company to go on a 200km cross country bike trip along the Kettle Valley Railway. Once everyone (10+ people) had a suitable bike and panniers (saddle bags), and cooking and cleaning equipment the only things left was to maintain about 8 bikes that were bought from local classifieds and un-tested. Buying 20 (two each for good measure) patch kits would not have been terribly expensive, but saving any cost is always good. Besides all the things that are in a patch kit were laying around my house.
Step 1: Materials and Tools
Most of the things you need can be bought at a hardware store.
Contact Cement (500ml or less)
Sandwich bags (1-2 per kit)
Sand Paper (1 square inch per kit) - optional
Old Inner tube (1 will do)
Spoon (disposable hopefully)
hammer and/or tin opener (or COLD chisel) to undo and do up the contact cement can.
Be careful when opening the can and read and follow the warning label on the contact cement.
Note if you're not using sand paper use sand from the location you're in instead, if you're location doesn't have any sand or gritty substances make sure to pack the piece of sand paper.
Step 2: Cut to Size
Start by cutting the inner tube and sand paper into smaller sizes. The Inner tube should be cut into patch like shapes, circles or ovals not squares and rectangles. Also when cutting the inner tube make sure to cut the final patch with the scissors on an angle so that the patch has beveled edges, slanting up to the center of the patch. The sand paper can be cut to whatever size is convenient, if you're using sand paper.
Step 3: Package Contact Cement
Take a spoon of contact cement (or less) and add it to the plastic bag. Squeeze all the air out or the cement will harden in the bag and then your stuck with a flat tire. Don't suck the air out with a straw, the contact cement is quite poisonous. Roll the bag up so it takes less space. I used a Ziploc bag and rolled and squeezed all the air out before sealing the last bit of the bag.
Step 4: All Together Now
Next add everything to a sandwich bag or just chuck the various components into your backpack or seat pouch. Squeeze the air out so it takes up less space.
Step 5: How to Use
If you've never had need to use a patch kit or this patch kit is a different kind then the ones your familiar with this is how to use it.
1- locate hole, this patch will only work on small holes so if your whole tire is blown up then you'll need a new one. The best way to find a leak is to first take the tube out of the bike, just like replacing a tube. Pump the tube up a little bit, listen and feel for ware the air is escaping. Run the tube around your ear when you hear something, move the tube down a little so you can feel the air on your cheek. A faster but less trail side way is to submerge the slightly inflated tube and look for bubbles. Also be sure to check the inside of the tire to avoid a re-puncture by the same object, mark with chalk (or mud) the location of the tire .
2- scratch up the patch and the tube, sandpaper is best but just plain sand or gravel can also do the job. Roughen up the area around the hole and the back (white) side of the patch.
3 - contact cement. Apply a little cement to the back side of the patch and the tire tube, less is more in this case just a thin layer will do. Next wait for the cement to get sticky, once it is sticky apply the patch. For more detailed info on how to use contact cement see back of the tin.
4 - wait a bit and then re-insert the tube into the tire and pump up, these patches if done correctly can last for years. One of my friends ran on four patches for two years, before selling the bike complete with patches.