How do you fill gaps in trim joints?

How do you fill gaps in trim joints?

Stick painter's tape above and below the gap for easier cleanup. Remove the tape immediately after applying the caulk; don't wait for the caulk to dry. Caulk that is 100 percent silicone can't be painted. Seal the tube of remaining caulk with a waterproof wire nut, duct tape or a golf tee.