How many doors you know?

To some extent, a door is the most important factors to ensure living safety. Till now, doors have numerous category. From materials, doors are divided into wood, steel, aluminium alloy, plastic doors and so on. From opening ways, they can be classified into flat doors, sliding doors, folding doors the turnstile doors, etc. From view of functions, doors can be divided into the gates, indoor doors, explosion-proof and fire-proof doors, etc.

Take a plywood door for example, it's a kind of door with light skeleton in middle and plywood, chipboard, moulding board on two sides. It is commonly used as indoor doors. Solid wood lines are usually set around the edges, which makes doors beautiful and tighten door shapes.

Though a plywood door has some advantages over processing and prices, it has some  shortcomings. As the plywood door is made in factories while door covers are made on site. Thus, chromatic aberration is possible to show between plywood doors and door covers. For another, the sound insulation effect of plywood door is poor, for the door is hollow inside with easy sound penetration. To have better sound insulation, you have to fill wood bricks into frames.