Mark A Take While Recording...?

Hello all,
I was reading the manual and came across the chapter "Mark takes while recording" (under the "Advanced Recording Techniques" section). So i set up the key command and tried recording takes and then used the key command on a selected take... I don't understand how it works, for the manual gives one just that much information. It says "This command places a tag in the current take, at the position the keyboard shortcut was used". But nothing seems to happen when i use the shortcut! I know I'm totally missing something here!
Any help would be much appreciated! Thank you!