Remove the old caulk. Using a putty knife and utility knife if necessary, remove all of the old caulking that surrounds your shower doors. This will be necessary around the bottom base and up the side walls also.
Clean the area around the shower door. Remove all caulking residue until you have a clean smooth surface. Use a nonabrasive cleaning solution so you don't accidentally scratch your tub or shower fixture.
Dry the surface around the shower door thoroughly with a dry cloth.
Load mold-resistant silicone caulk into a caulk gun. Cut the tip of the caulk tube, using a utility knife, to the appropriate width needed for the resealing process.
Apply the caulk. Run a thin line of silicone along the outside of the shower door track by squeezing the trigger of the caulk gun to dispense the silicone. Immediately smooth the silicone with a caulk finishing tool to create a smooth line around your framing.
Apply the caulk to the inside of your shower door framing. Immediately smooth the silicone with the caulk finishing tool as you did the reverse side.
Allow the silicone caulk to dry according to manufacturer’s directions before getting it wet.