I regularly go hunting and my binoculars are an important item to take. It's necessary to use lens caps to keep water, dust and bits of leaves from getting on them. But lens caps are a pain. They are easy to lose, take time to remove and store and make unnecessary movement that might scare the animals.
To solve the problem I have fashioned tethers for the lens caps out of a bicycle inner tube.

Step 1: What You Need

1) Bicycle inner tube
2) Lens caps!
3) A sharp craft/utility knife. The sharper the better. A clean cut means the rubber is less likely to tear.
4) Clamps
5) Hole punch. I used a plain old office paper punch but you can use a leather punch or anything similar. Something that will make a smaller hole than my paper punch will probably give a better result
6) Metal straight edge or ruler
7) A coin (optional)

Step 2: End Caps

The trouble with inner tubes is that they are round and we want it to be straight!
Use the clamps to straighten the tube. Don't stretch it, just straighten it. Now cut the inner tube open and unfold it.
Cut a rectangular strip out of the rubber. A 20mm width worked for me -- twice the depth of the cap. A length of 180mm worked for me. You might need to experiment if your binos are larger or smaller than mine.
The corners should be rounded. I used a coin and cut around it.
We need to cut slits in the rubber strip which will stretch around the binos and lens cap. To stop the rubber ripping we use the hole punch at each end of the slit.
Punch a hole at one end of the strip equidistant from the sides and end. We will cut a slit the same length as the diameter of the cap, so use the cap to measure where to punch another hole. Finally, using the straight edge, cut a slit between the two holes.
Now do the same at the other end. This time the length should be the diameter of where the tether sits on the binos.
Carefully stretch the rubber over the end of the binoculars and the end cap.

Step 3: Eyepiece Cap

On my binoculars I have one cap for both eyepieces so it made making a tether slightly more difficult.
I guessed how large to make the slit for the cap and stretched it out sideways when fitting.
At the other end I cut a slit right to the end. This wraps around the centre shaft. I wrapped it with insulation tape to attach it there firmly.

Step 4: Final Notes

The rubber tether fits snuggly around the caps but if they are a little loose you can use some Ados F2 adhesive (or similar) between the rubber and cap.
They are easy to use, simply pop off and don't worry about losing them!
I hope someone finds this instructable useful!