Compass

A compass in a module slot. It holds the cut in one direction.

Locked at 168°, needle green	The CRT's antennas light up

What it does

K locks the cut in the direction you look, at any angle (a diagonal tunnel works). K again lets it follow your view.
A needle at the top of the picture shows where the cut points, with the bearing in degrees (0° = north).
When you face that direction again, the needle turns green and thick with a clink, and the antennas of the CRT in your hand light up.
A lodestone compass points the cut at its lodestone. In another dimension the needle spins.

With "Color blind colors" on in the settings, the needle turns blue instead of green.