What it does
The belt machine cannot get closer to a wall than its own housing, so a band around every room, under every radiator and into every doorway is sanded with a disc instead. A disc cuts in a circle; a belt cuts in a line. They leave different scratch patterns on the same wood.
Blending those two patterns so the join is invisible is the skill in the job. It is done by stepping the edger through the same grit sequence as the big machine and then blending both with a multi-disc machine before any finish goes near the floor.
Why it matters to your floor
- The 'halo' — a visibly darker or cloudier band around the edge of a refinished room — is the most common defect on an otherwise decent refinish, and it is an edging failure. It appears because circular scratches hold stain differently from linear ones, and it is permanent once coated.
- It is also the defect most visible from a doorway, which is where anyone standing in a hall looks first.
What happens without it
Edging at one grit and going straight to finish, or skipping the blend entirely.
A dark ring around every room. The only fix is resanding the whole floor, so it is worth more attention at quote stage than almost anything else on the estimate.
How to tell, before you sign
- Look at a finished job at the wall line and in the doorways, not in the middle of the room. Then look at the same floor under a window.
- Ask specifically how the edge is blended into the field. 'With the buffer' is the right shape of answer.
These questions are meant to be asked of everyone quoting you, not only of us. A trade that cannot answer them is telling you something useful.