Jef Maynard was the prop builder (or "Toolmaster") for Mystery Science Theater 3000.

Maynard was hired at the start of MST3K's second season on the Comedy Channel, and Frank Conniff (who had been hired as a writer at the same time) got into the habit of singing "Toolmaster Jef Maynard" to the tune of the Trip Shakespeare song "Toolmaster of Brainerd". The nickname stuck to the point where "Toolmaster" eventually became Maynard's official title, and he was listed as such in the show's closing credits.

He is also known for potraying Crow's doppelganger Timmy in the episode Fire Maidens of Outer Space.