| 摘要 |
<p>A level (100) comprises an elongate one-piece frame (120) with a hollow interior defined by two sidewalls (180) extending between top and bottom horizontal walls (130, 140), each horizontal wall (130, 140) defining corresponding top and bottom parallel measuring surfaces and top and bottom interior surfaces; a topnotch (20) formed by removal of a topwall section and adjacent sections of sidewalls; and a central vial (50) within the topnotch (20).</p> |
