12.3 Using Transient Mark Mode Momentarily

If you don't like Transient Mark mode in general, you might still want to use it once in a while. To do this, type C-<SPC> C-<SPC> or C-u C-x C-x. These commands set or activate the mark, and enable Transient Mark mode only until the mark is deactivated.

C-<SPC> C-<SPC>

Set the mark at point (like plain C-<SPC>), and enable Transient Mark mode just once until the mark is deactivated. (This is not really a separate command; you are using the C-<SPC> command twice.)

C-u C-x C-x

Activate the mark without changing it; enable Transient Mark mode just once, until the mark is deactivated. (This is the C-x C-x command, exchange-point-and-mark, with a prefix argument.)

One of the secondary features of Transient Mark mode is that certain commands operate only on the region, when there is an active region. If you don't use Transient Mark mode, the region once set never becomes inactive, so there is no way for these commands to make such a distinction. Enabling Transient Mark mode momentarily gives you a way to use these commands on the region.

Momentary use of Transient Mark mode is also a way to highlight the region for the time being.