This apparatus is used to measure the deformation in elements of structure. Whenever a load is applied to a simple bar structure, its members undergo a strain. This unit consists of a base structure which provides the support locations for the truss. Three metallic elements form a truss in a triangular shape. Load is applied from the top of the truss structure via a hanger. Each member has a force gauge connected to it which shows the forces produced due to applied load in each member. This apparatus represents a simple roof truss bar structure. In the single plane system the bars are only subjected to compression and tension. Loads are applied only to the nodes. The unit comprises three members that are joined together using node point such that the joints are free to move. A longitudinally adjustable base members permits the structure to be constructed with different angles. The bars engage in the nodes by quick locks. Two of the node points also form the supports (fixed and free with bearings) and are clamped to the sturdy aluminum section base frame. The external load is applied to the upper nodal point by means of weights. The bar forces occurring are measured directly on force gauge in the middle of the bar. The method of joints enables the bar forces to be determined by formulating a system of equations.