Leggett and platt mattress retainer. The leggett and platt 50 series is perfect for an entry level adjustable base. Experience the benefits of an adjustable foundation at an affordable price. View and download leggett platt style series owners manual online. This latest version of sertas popular value priced adjustable foundation allows you to adjust the head and foot of your mattress so you can find the level of comfort and support thats just right for you.