Gyro lets you set up macros (lists of commands) to be run whenever you join or leave a raid, for convenience or laziness. You can, for example, enable raid UI mods only when you're actually in a raid, disabling them when you're done.
It's easy to set up: put commands you want to be run whenever you join a raid in the GyroStartRaid macro, and the commands you want to be run whenever you leave a raid in the GyroEndRaid macro. (Gyro creates these macros for you automatically.)
For example, if you want CT_Timer to only show up when you're in a raid, use these macros:
GyroStartRaid:
/timer show
GyroEndRaid:
/timer hide
More details are in the Readme file that comes with the mod.