You can also use a #5 (size?) plumbers rubber plug. I carry one in my case all the time and use it toward warming my drone reeds at the beginning of my practice -- which is more of an old cane habit considering I've been playing synthetic for the past ?11? years. Take out your chanter, seat it snugly in your chanter stock, and strike-in. Depending on the bag seasoning you use, if you pick up one of these, pick up a total of 5 -- when seasoning, plug off all stocks but one, pour your bag-sauce in, cork off the last stock and go to work treating your bag. The next size up plugs will also work but are a bit big -- the #5s go in/out more easily.

...and when your piping friend isn't looking, stick one of these in the bottom of their chanter -- muted chanter surprise can be high-Larious.