As time goes by eventually your archery targets will get holey (or fall down) in which case you either need to replace the material or repair it in some manner.
Repairing Natural Tentest Targets
In the case of Natural Tentest targets, like those at the Toronto Archery Range located at E. T. Seton Park shown above, one way to repair the big gaping holes is to wait until one of the target butts collapses and falls down - often due to heavy rain and/or wind - and then you can use the broken fallen pieces of Natural Tentest to stuff the holes in the other targets.
And for fun, you can also add a large water container to the target butt which collapsed so that people can still potentially shoot at something until that target's tentest is replaced.
Repairing 3D Targets
In the case of 3D targets (deer, raccoons, etc) that are popular with hunters one of the best ways to repair them is with foam, like in the video below. What brand or style of foam you use doesn't really matter, what is really important is that you don't overfill the holes you are repairing because otherwise excess material will leak out (as demonstrated in the video below). A "less is better" approach is best for that scenario.
Repairing DIY Cardboard Targets
The beauty of cardboard targets is that they're super easy to repair and cost effective. Just make a habit of saving any large pieces of cardboard from your home and/or workplace and you can easily just rip out any damaged pieces of cardboard from your DIY targets and replace with new cardboard.
Best of all, the old cardboard is still recyclable so it has simply been reused before eventually reaching the recycling bin.
Your cardboard archery target doesn't need to be fancy either (like the one in the image below). It simply could be a cardboard box which is filled with cardboard. Having a wooden frame is really unnecessary for most people's purposes. But once you have a cardboard target they're very easy to repair.
