A pocket penetrometer can be used in field investigation to verify the visual classification of fine-grained soils. It consists of two telescopic cylinders containing a compression spring. A cylindrical tip, screwed onto the lower part of the body, is pushed into the soil, compressing the spring. The indicator sleeve retains the reading after the piston is released. The value of the unconfined compressive strength (UCS) can be read directly from the instrument’s graduated scale. This value is derived from the force required for indentation. The measured resistance values can assist in the classification and description of cohesive soils and provide useful preliminary information on undrained shear strength.