The disclosure depicts an adjustable square device with a body having a substantially uniform cross-section at planes orthogonal to a longitudinal axis, the cross-section having a generally rectangular outline. A first groove extends inwardly from a first end of the body and oriented generally parallel a bottom surface of the body. A second groove extends inwardly from the first end and is orthogonal the first groove, the first and second grooves intersecting at a vertex. The device also has a tunnel extending from the vertex to a second end of the body, and a blade slidably engagable into one of the first or second grooves.