The Handyman's Pocket Book: Draught Excluders.

Much can be done by shifting the stops as in Faults In Room Doors, but if the door has shrunk considerably in its width one of the copper strip excluders can be used.  At the floor either one of the proprietary excluders can be fitted, or a ramp can be used as in Fig. 1.  Note the slight rebate which helps to exclude draught.  Oak or another hard-wearing wood should be used.