| 摘要 |
A standard three foot carpenter's level with two sleeve-like extensions adjustably movable upon it to provide accurate plumbing and trueing facilities to six foot-six inch and eight foot lengths. The top and bottom surfaces of the base level have projections which fit into top and bottom interior surface slots in the extensions to prevent transverse motion between the base level and extensions while minimizing surface contact and wear between the two. A centered slot in each of the two opposing side walls of each extension limit the contact with and wear between those walls and the mating flat side walls of the base level. The front face of the base level contains a pair of depress buttons to engage apertures in each extension to set the 6'6'' or 8' length. The base level contains three bubble vials, one at the midpoint and the other two equal distant from and on opposite sides of the mid-point vial. The extensions have a pair of semi-circular openings which meet about the mid-point vial, or partially encircle the other two vials in the base level corresponding to the 6'6'' or 8' extension modes. Each extension has a spacer block movably secured to a slot in its bottom surface to permit the extension level to avoid most irregularities in the surfaces of construction materials being plumbed or trued.
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