For drawer rack, the bottom part can not only store goods, but also be the supporting column of the upper construction bearing beam. Normally it can be several tiers (commonly 2-3 tiers), with walking stairs, handrails and loading gates, etc. It is best for the high-bay warehouse with small goods, manual picking and big storage capacity with different types, also goods for old warehouse renewal, it can improve the storage capacity. If the span decreased for the bottom bearing beam, the construction cost will be lower greatly.