| 摘要 |
A level comprises an extruded thin wall frame structure having an opening of I-shaped configuration extending from end to end thereof. The thin wall frame structure includes a pair of elongated operative walls each having a pair of transversely spaced inwardly turned flanges defining the width thereof and an exterior operative surface extending between the flanges thereof. The operative surfaces are planar and parallel. A pair of angular walls extend from each pair of spaced flanges in converging relation with one another and a pair of central walls are spaced apart in the direction of the width of the operative walls a distance less than the width of the operative walls and integrally interconnected between the pairs of angular walls extending from the flanges. The operative walls and the central walls having a plurality of wall openings therein.An end member closes the opening at each end of the thin wall frame structure. Each end member has structure constructed and arranged to cooperate with the configuration of the thin wall frame structure to fixedly secure each end member in closing relation with respect to the associated end of the thin wall frame structure. A level indicating vial system has structure constructed and arranged to cooperate with the configuration of the thin wall frame structure to fixedly secure the level indicating vial system therein.
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