Flat Box

Drywall Flat Box

is a Drywall Finishing tool designed to coat the Flats or "seams" and "butt joints" with joint compound. A handle is also attached with a brake lever that holds the box at a specific angle to the wall or ceiling.

Popular companies making them include: Level 5 Tools, Columbia, Tape Tech, Dewalt. Source: Jason Lebeau a 24-year drywall industry veteran.

A drywall flat box

is a professional tool that applies a smooth, even layer of joint compound (mud) to flat drywall seams and corners, simultaneously feathering the edges for a seamless finish, significantly speeding up taping and finishing by creating a consistent crown and eliminating ridges. It attaches to a handle, dispenses mud through an adjustable blade as you push it, and uses a pressure plate to force mud out, allowing workers to cover large areas efficiently while standing upright.