Bring a 12-quart pot of water to a boil. Add the garlic, crab boil seasoning, lemons, and beer. Using tongs, add the crabs one at a time to the pot. Cover and return the pot to a boil and continue to boil for 20 minutes.
Remove the crabs one at a time with the tongs to a serving platter. Sprinkle with more crab boil seasoning, serve, and enjoy.