This nonfiction follow-up to Whose Truck? features six kinds of specialized rigs used to construct a light-rail system--a tunnel borer, an excavator, a bulldozer, a tie dragon, a tamping machine, and a bucket truck--with five different parts of each rig properly labeled. The answer to each inquiring refrain of "Whose rig is this?" is revealed under a gatefold, engaging the reader in an informative guessing game about construction machines and their operators. With lyrical (and factual!) rhyming text by New York Times bestselling author Toni Buzzeo, and the expertly stylized art of Ramon Olivera, this sturdily constructed board book is perfect for curious and playful young readers.