English英语译成Chinese汉语 科学 电脑（总称）

Only BRAND NAME can deliver a tightly integrated hardware and software solution that’s so powerful and easy to set up and use. Everything you need is already in the box.
Inside, you’ll find quick-deployment rails for fast and easy installation and deployment. The rail design supports a wide variety of four-post racks and cabinets, letting you use PRODUCT NAME with existing gear.
句中的rails是什么意思？four-post racks 也不好理解。