The trim covers the lap joints and locks the boards in place to stop separation on uneven floor. The trim pack contains pre-drilled three-1/four inch huge top rails and corner moldings that attach into the raised mattress with bundled screws. Our impressions with the Jumbl raised garden bed are that https://zanderbeefe.westexwiki.com/707228/an_unbiased_view_of_cedar_for_raised_garden_beds