The plastic/rubber thing set into the ground in a baseball field to mark where a player must touch to score after running the other three bases. The strike zone is also delimited with the help of home plate. Roughly shaped like a single-gabled house turned upside-down:
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In the terminology of teenage physical intimacy, to make it to home plate (or home base) means to go all the way, score, get some, have sex. Come to think of it, the shape of home plate could be mighty suggestive...