A sealing plug for a block-and-tackle balance comprises a sealing member having an outer periphery shaped so as to conform to an inner surface of a channel of a window jamb in which the block-and-tackle balance is accommodated. An opening is defined in the sealing member allowing a cord of the block-and-tackle balance to pass therethrough such that the cord is movable with a movement of a window panel. A connector configuration in the sealing member and allows the sealing member to be releasably secured to a bottom end of the block-and-tackle balance.