A beam balance is a device used for the determination of the mass of a body under gravitation. It consists of a beam supported at the center by an agate knife edge resting on a support moving inside a vertical pillar. The beam carries a light pointer which moves over a scale. There are two stirrups at the ends of the beam which carries two scale pans of equal masses along with adjusting nuts. These can be adjusted to make the pointer to oscillate within the scale when the balance is raised. The balance is mounted on a platform provided with three leveling screws so as to make the pillar vertical. There is a plumb line which shows whether the pillar is vertical or not. The balance is enclosed in a glass case in order to avoid disturbances due to air.
This video explains how to find the mass of the given body by sensibility method, using a beam balance.