Finding a mouse entry point means following actual travel routes and openings instead of sealing randomly. The most useful places to inspect are material joints, utility penetrations, doors, garages, and areas where droppings or rub marks appear.
Start from the freshest indoor evidence
Fresh droppings, gnawed food, or trap activity shows which area the animal is using. From there, follow wall edges toward cabinets, pipes, and openings rather than giving every part of the house equal priority.
Inspect the corresponding exterior area
Check around pipes, cables, vents, siding transitions, and doors. Mice can use surprisingly small gaps, so finding a continuous route indoors matters more than measuring one isolated opening.
Use light and tracking clues without attracting mice
A flashlight from different angles can reveal gaps and rub marks. In controlled dry areas, a small tracking patch can show travel, but do not place food beside an exterior opening because it can attract additional activity.
Seal after confirming the route and controlling activity
Use rodent-resistant materials appropriate for the opening and building assembly. Before closing an active cavity, make sure you will not trap animals inside and coordinate exclusion with the control plan.
Sources
- U.S. Environmental Protection Agency — Integrated Pest Management — Integrated pest management using sanitation, exclusion, monitoring, and targeted control.