Compass Parts & Function

To take a bearing, turn the housing, then rotate your body until the red needle sits inside the orienting arrow — “the needle in the shed.”

How the parts work together

1Lay the baseplate edge on the map from where you are to where you're going, direction-of-travel arrow toward the destination.
2Turn the housing until its orienting lines line up with the map's north–south lines (dial north toward map north).
3Read the bearing at the index line — that's your direction in degrees.
4Lift the compass, hold it level in front of you, and rotate your whole body until the red needle sits inside the orienting arrow ("needle in the shed").
5Walk the way the direction-of-travel arrow points, re-checking as you go so you don't drift.

Remember it as

Red in the shed, then go ahead.

Every bearing you take or follow — the parts are the "grammar" behind the bearing, declination, and orienting-the-map skills.
Orienteering, hiking off-trail, and relocating yourself with map and compass.
Understanding why the steps work, not just memorizing them.

Keep the compass away from metal and electronics. A knife, phone, belt buckle, car, or power line pulls the needle and gives a false reading — check well clear.
Hold it level. A baseplate needle must swing freely and flat — tilt it and the needle drags and misreads.
Trust the needle, verify with terrain. It points to magnetic north reliably, but confirm your position against the land so one bad reading doesn't send you far off.
Know red-north. Following the wrong (south) end of the needle sends you exactly 180° backwards — the red/marked end is north.
Magnetic ≠ true north. The needle points to magnetic north, which differs from map north by the declination for your area.
A compass has no batteries and no signal — that's its strength. Carry it and know it as a backup to any GPS.

"Put the needle in the shed." Box the red needle inside the orienting arrow (also called the doghouse) — do that and the direction-of-travel arrow is your heading.
The parts named. Baseplate (the clear body with ruler edges), bezel/housing (the 0–360° dial), orienting arrow and lines (inside the housing), direction-of-travel arrow (on the baseplate), and the index line (where you read the bearing).
Why the baseplate is clear. You set it right on the map and read the lines and features through it — what makes an orienteering compass so quick to use with a map.

Compass use appears in the Scouts BSA navigation requirements and the Orienteering merit badge.