Communicating the (pencil) point of pest exclusion


May 19, 2021



Most of us were introduced to the archetypal yellow, No. 2 pencil in elementary school.

We learned how to properly use them (write your name, but don’t use it to poke your classmate) and care for them (walk, don’t run to the pencil sharpener at the rear of the classroom). By the time high school arrived, most of us graduated to pens, except for filling in bubbles on standardized tests.

But there’s one more use for a pencil that I bet you weren’t taught in school: pest exclusion inspections.

We all know that a common-sense approach to structural pest management typically includes making recommendations to your client about sanitation and exclusion.

By eliminating or reducing the available food, entry points and harborage locations for pests, control efforts can be synergized and risk of future infestations can be reduced. Cleaning up pest food sources in an account has its own challenges, but illustrating what a quarter-inch gap looks like to a client with a mouse problem can be daunting. Fortunately, it turns out the trusty, No. 2 pencil is just what you need.

A standard No. 2 hexagonal pencil is cut to a hexagonal height of about 9/32 of an inch, very close to the quarter-inch height of the skull of the average house mouse (Mus musculus).

Just like structural pests, pencils are ubiquitous:

An estimated 2 billion pencils are manufactured each year for use in the United States. If your clients don’t have a pencil of their own, share yours (another skill you learned in grade school).

Ask clients to follow you on a quick pest assessment, and have them compare the diameter of the pencil to potential pest entry points. Does the pencil fit in a gap under a door? Repair or install a door sweep. Does it fit in a crack in the foundation or under a baseboard? Seal the space.

By demonstrating what a pest entry point really looks like by using an object your client is familiar with, you can expect more cooperation and better results from your pest exclusion efforts.

About the Author

Dr. Jim Fredericks, PHOTO: National Pest Management Association

You can reach Dr. Fredericks, BCE, executive director of the Professional Pest Management Alliance (PPMA), at

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