Caulk keeps a house tightly sealed. It should be applied where different materials meet like window and door frames. It is your best bet for cracks thinner than a pencil. For best results, apply a small bead and smooth it out with a moistened finger as you work.

First, clean out any old caulk or debris. Then cut the tip off the tube of caulk, place in a caulk gun and begin to apply, holding the gun at a 45 degree angle. Once applied, moisten your finger and smooth the caulk.

Image adapted from Reader's Digest(1982), Home Improvements Manual