Fill a spray bottle with hot water. Add 1 tbsp. baking soda to the water. Screw on the top and shake the bottle to disburse the baking soda.
Spray the baking soda solution generously over the wallpaper border adhesive. Allow the mixture to remain on the adhesive for 15 minutes to loosen the glue.
Wipe the glue from the wall with a damp sponge. If the adhesive remains on the wall, reapply the baking soda solution and wait 20 minutes.
Rinse the sponge in a bucket of warm water as you remove the glue from the wall to keep from redistributing the glue back onto the wall.
Wipe the walls dry with a clean cloth after removing all adhesive.