A balance with a helical rod generating vertical thrust in conjunction with a spring for the sashes fitted to vertical sliding windows Balansveer, Patentveer

There are several ways to help the top half of a double hund window stay up, and make it easier to open and close. Old windows use a lead weight on a rope held inside a pocket cavity in the wall. A spiral balance uses a metal rod that that has spiral groves in it that works against a gear on the sash; sort of like a bolt and not. To read more on Spiral Balance.

Used in many inferior windows, this type of balance requires periodic adjustment and lubrication and can become more difficult to operate over time. We strongly recommend purchasing a window with a block and tackle balance system for a lifetime of smooth operation. Compare a spiral balance with Harvey's Block & Tackle Balance.