As I mentioned yesterday, when working in the arrangement view the loop brace is used to set the boundaries for both looping and punching. For my money, the easiest way to set these boundaries is using the Loop Selection command.
First highlight a clip or region of time:
Then, from the Edit menu (you’ll definitely want to learn the keyboard shortcut for this one!):
This command will place the brace around your selection, and turn on the Loop Switch:
If you’re regularly using this command to set punch points, it’s handy to have a keyboard shortcut for turning the Loop switch off. By default, there isn’t one, so you’ll have to create it yourself in the Key Map.
Above you’ll see that I’ve mapped the letter “l” to the loop switch. You may also find it handy to map the punch in and punch out switches as well.