When building the wall, the reserved hole shall be about 20mm larger than the length and width of the distribution box. When the distribution box is buried by masonry, the. When the distribution box is installed on the wall, it should be fixed with split bolt (expansion bolt). The bolt length is generally the sum of the embedded depth (75-150 mm), the thickness of the box bottom plate, the thickness of the nut and washer, plus the "head allowance" of about 5mm. It takes the incoming power and safely distributes it to different circuits throughout your building. This article mainly talks about the first one. An electrical distribution box, also known as a power distribution box, panelboard, or consumer unit. The distribution box (DB box) helps safely and efficiently distribute electrical power.