For decades plywood was the go-to inexpensive wood of choice for many home-repair projects. In fact, it was actually the first manufactured wood product available. Then the term MDF, or medium-density fiberboard, started making its way onto home-improvement shows and among do-it-yourselfers, making it a popular material in recent years. Still, many people do not know the differences between these types of wood products.

Plywood is constructed by gluing several layers of thin wood veneers between two pieces of wood to create a solid sheet. Experts say there is an odd number of veneer layers, and each one is attached at a right angle to the one below to add strength to the plywood. There may be knots or irregularities in the plywood because it is made of actual slices of wood. It comes in a variety of strengths, depending on the thickness of the plywood. Thickness can vary by sheet depending on the manufacturer, so each sheet may not be consistent.

MDF is formed with wood fibers or shavings mixed with glue or resin. Under heat or pressure, the MDF is made into a solid material. Because MDF is not made from slices of wood to form veneers, it will not have the traditional graining or knots associated with wood. This can be an advantage or disadvantage depending on how it is ultimately used. MDF is often easy to cut, drill and manipulate because users will not have to work around grain or knots. But users should be careful to drill pilot holes before attaching MDF because it can split. Due to machine creation, MDF is generally uniform in thickness, which makes it consistent for many uses. It is important to note that sanding and cutting of MDF can cause the release of formaldehyde. Safety goggles and a mask are a must when using this product.

Plywood is more readily used for walls, ceilings and subfloors because of its strength. MDF is widely relied on for building cabinets, crafts, shelving and trimwork.