The Knickerbocker bolt on Rails have a center support that can be accomodate a queen & king size mattress and foundation. 

Knickerbocker is America’s premier manufacturer of stylish and attractive heavy duty bed frames and bedding support systems. We are a fourth generation family owned and operated company in business since 1919. Knickerbocker remains the only bed frame supplier committed to manufacturing all of its products here in the United States.