It’s sited in a classic schoolhouse, but the Barnegat Light Museum allows guests to use a “Cheat Sheet” during the museum’s extended hours this summer.

The two-page “Cheat Sheet” primer on treasures points out that the prismatic first-order Fresnel lens formerly topping the Barnegat Lighthouse weighs 3 tons and took six weeks to reassemble in its current home, at 501 Central Avenue.