| 摘要 |
<p>A level comprising: a frame having at least one plane measuring surface and at least one side at right angles to each other and designed to retain a bubble level vial so that the bubble level vial is visible from the side; a bubble level vial affixed within the frame so that its long axis is parallel to the plane measuring surface; and level indicating indicia on the side. A level vial useful in construction of such levels comprises; a transparent unmarked container; a fluid incompletely filling the container; and a bubble of air within the container.</p> |
