Abstract: A carpenter's level extendable preferably from a length of 24 inches to a length of 48 inches in six-inch increments is described. The level includes an I-beam shaped base section with right and left extension members slidably mounted thereon. Said extension members engage either side of the base at tracks formed by the side extensions of the I. The extension sections are independently movable relative to the base and to each other, and a locking mechanism is carried by each extension section to lock said section against lateral movement in a predetermined extension position. Each extension section carries a conventional tubular spirit level vial in an aperture and a third vial is centrally located in an aperture through the base section. Each extension section and the base section also has apertures therethrough spaced on, for example, six-inch centers for visible observation of each vial whether the members are extended or collapsed.