Abstract: A multiple-movement, single clamp, implement-positioning device is constructed to permit sliding movement of the base portion of a main body member on a guide rail. An upper portion of the main body member is rotatably mounted on the base portion and includes a hollow chamber with a compressible sphere pivotally mounted in it. The compressible sphere has a bore through it; and an elongated cylindrical shaft is slidably and rotatably mounted in the bore in the compressible sphere. A single control member, in the form of a threaded rod, extends through the top of the upper portion of the main body member to engage the sphere to compress it into engagement with an extension on the base portion. This compresses the bore around the shaft, locks the pivotal rotation of the sphere, locks the upper portion of the main body member to the base portion and the base portion to the rail on which it is positioned.