horizontal vial has 2% slope. This is the latest in vial
technology: vial installed blank, aligned by a computer
and etched by a laser. Thus even the 2% slope is accurate
to 1/64” per yard.
|Permanent magnets are much stronger
and more durable than strip magnets.
||The only plumb vial that can be
read from the top. This is a robust horizontal vial installed
as a vertical vial.