Lumber edge glued into a solid slab is considered Lumber Core also known as Block Core. Lumber Core plywood is most often found in the construction of import panels, usually only 18mm thickness panels. Lumber Core plywood consists of a face & back veneer, then a layer of cross band veneer, with the edge glued lumber in the center. Lumber Core plywood should be used for the bending strength and screw-hold ability. The ability of Lumber Core plywood to bounce back makes it an excellent choice when constructing long or wide shelves in cabinets or closets.This type of core is a tad pricey and because of that it’s not widely used and rarely found at your local supply.