| 摘要 |
A level tool is arranged to facilitate gradient measurement and matching of lines on inclined surfaces, such as to establish parallel reference lines when installing roofing materials. The tool has a rule-like base member defining an elongated reference edge, and has a centrally located protrusion on its lower surface and a level on its upper surface for sensing orientation of the tool around an axis perpendicular to the base member and to the level. The level can have a fluid filled disk or circularly arched tube with a captive air bubble, and preferably is graduated to mark positions of the bubble. The tool is placed on the inclined surface so that the raised protrusion rests against the inclined surface and a reference edge is parallel to the plane of the surface and aligned to a pre-existing line to be matched with a parallel line. The protrusion avoids the influence of bumps in the surface and allows the tool to be rolled transversely to bring the reference edge near or against the pre-existing line while tilting the level to move the bubble radially outwardly. The orientation of the tool is noted from the bubble position. When the tool is moved to a new location, set on the protrusion and oriented as noted, the reference edge is oriented to a line parallel to the pre-existing line.
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