Construction UL GREENGUARD Certified to contribute to healthier indoor air, keeping you and your family safer. We use a variety of premium hardwoods for this bed including solid pine, poplar, rubberwood, birch veneers, premium-quality plywood and MDF. Each finish is thoroughly applied by hand in a multi-step process. Bed has a slat roll foundation and can fit most standard mattresses. Add the trundle and trundle mattress (both sold separately) to Twin and Full size beds for instant sleepover space. Queen size bed has center legs for additional support and cannot accommodate a trundle. Top bed uses a standard (L x W) mattress. Bottom trundle fits our trundle mattresses. Do not use boxspring for bed or trundle. Trundle provides a comfortable extra bed for overnight guests when used with a ma