On a double hung window both sashes “tilt” inside for cleaning ease whereas on a single hung only the bottom s
ash tilts in for cleaning. Hung windows rely on mechanisms referred to as balances. Balances allow
Depending on manufacturer’s specifications one or two cam locks are standard. Double hung windows will come standard with a “night lock”. A night lock allows your window to maintain airflow while preventing the window from being open all the way for security purposes. When closing all windows will have an interlock system.
An interlock is where the two sashes meet in the locking position. Interlocks should be weatherstripped. Some interlocks will be reinforced by aluminum or fiberglass to prevent bowing of the sashes in the future. The fiberglass reinforcement is non-conductive yet maintains superior strength.