Some of the older types of brooms have a separate hydraulic cylinder at each end of the broom, which raise and lower the brush assembly. These cylinders are operated with separate controls. Sometimes, the two cylinders do not exert even pressure, causing one end of the broom to exert heavy pressure on the pavement while the other end barely contacts the surface. This is not a problem with newer models, since they are now manufactured with single controls. If an older model is being used on the job, care should be taken to watch for uneven pressure at opposite ends of the brush.