Inventory Trick on Minecraft Java

so I’ve seen YouTubers when there making a build, use up a stack of there cobble (or any type of block their using) and then do some type of hotkey or something and get another one from there inventory. Without opening their inventory… I thought it might be useful to know that since it would be convenient, and I’m doing a few builds where it would be useful. If anyone knows the trick, if you could share it that would be awesome!