Planks - Vertical boards that extend the full height of the door, and are placed side by side filling the door's width. Battens - Smaller slats that extend horizontally across the door which the planks are affixed to. The battens hold the planks together. Sometimes a long diagonal slat or two are also implemented to prevent the door from skewing. On some doors, especially antique ones, the battens are replaced with iron bars that are often built into the hinges as extensions of the door-side plates.
Ledged and braced doors Consists of vertical tongue and grooved boards held together with battens and diagonal braces.Frame and filled door Consists of a solid timber frame, filled on one face, face with Tongue and Grooved boards. Quite often used externally with the boards on the weather face.Flush doors (many modern doors, including most interior doors)Stiles and rails - As above, but usually smaller. They form the outside edges of the door. Core material: Material within the door used simply to fill space, provide rigidity and reduce druminess.
Hollow-core - Often consists of a lattice or honeycomb made of corrugated cardboard, or thin wooden slats. Can also be built with staggered wooden blocks. Hollow-core flush doors are commonly used as interior doors.
Lock block - A solid block of wood mounted within a hollow-core flush door near the bolt to provide a solid and stable location for mounting the door's hardware.
Stave-core - Consists of wooden slats stacked upon one another in a manner similar to a plank & batten door (though the slats are usually thinner) or the wooden-block hollow-core (except that the space is entirely filled).
Solid-core - Can consist of low-density particle board or foam used to completely fill the space within the door. Solid-core flush doors (especially foam-core ones) are commonly used as exterior doors because they provide more insulation and strength. Skin - The front and back faces of the door are then covered with wood veneer, thin plywood, sheet metal, fiberglass, or vinyl. The wooden materials are usually layered with the grain alternating direction between layers to prevent warping. Fiberglass and metal-faced doors are sometimes given a layer of cellulose so that they may be stained to look like real wood.