请教:open brick

在关于隔离式散热器的文章中,有一句话是这样的:The arrangement in the upper (e.g., easy replactment,easy change in rating) with isolated heat sink concept for totally enclosed designs.It has quite aptly been called the "open brick" model.请问所谓"open brick" model在专业术语中是一种什么模式呀?