9c2787c1_he_Beat__A_Blog_by_PremiumBeat__Description
[Command] Range Selector [Shortcut] r [Description] 
The Range Selector allows you to select a range that spans a portion of a clip or multiple clips. You can mark these ranges with ratings and keywords, apply effects to them and modify them in other ways.
Final Cut Pro X Shortcuts - The Big Cheat Sheet - The Beat: A Blog by PremiumBeat
Description