The Model A-9 Retrievable Extensometer (Patent No. 5,585,555) is designed to measure deformations in boreholes in rock, concrete, and other construction materials. The device can be used in pile load test studies, plate jacking tests and virtually any application where a hole can be drilled or a pipe can be cast into the structure being studied. The system features adjustable gauge lengths, rapid and simple installation/removal and high accuracy using a variety of transducers including Vibrating Wire and DCDT’s. Adapters for use in square tubing are also available.