Pay particular attention to the bottom corners as this is often where rodents and insects enter. Apply caulk along bottom outside edge and sides of door thresholds to exclude ants and other small insects. Gaps under sliding glass doors can be sealed by lining the bottom track with foam weather-stripping. These are common entry points for such pests as rodents, ants, spiders and yellow jackets. Holes can be plugged with caulk, cement, urethane expandable foam, steel wool, copper mesh or other suitable sealant.
Caulk cracks around windows, doors, and fascia boards.
Use a good quality silicone or acrylic latex caulk. Although somewhat less flexible than pure silicone, latex-type caulks clean up easily with water and can be painted. Caulks that dry clear are often easier to use than pigmented caulks since they don't show mistakes. Buy a good caulking gun. Prior to sealing, cracks should be cleaned and any peeling caulk removed to aid adhesion.