Many styles of ascenders (especially if they’re a few years old) have two holes near the bottom. One is a big one that can fit a carabiner, and the other is a small one that can fit . . . pretty much nothing.
(I'm sure the clever engineers at Petzl thought it was a good idea to put this little hole here, but they didn't tell me why. :-)
Here's a small enhancement you can do to make this little hole more helpful. With a foot or so of webbing, tie a small loop directly through it. Some people like to put a quick link in it instead. By adding a webbing loop or quickLink, you create a second point of connection for a carabiner.
When you have this, you can use the primary hole to clip your daisy chain with locking carabiner, and this secondary webbing connection to clip your aiders with a non-locking carabiner.
Or, if you use a Grigri for an ascending system, you can put a pulley or a carabiner on this webbing to give yourself a downward pull and a little mechanical advantage when you’re ascending. Personally, I prefer the webbing, because it can twist under load and gives a slightly more efficient pull if you're using it with a pulley.