求翻译：12． 当吊灯自重在3kg及以上时，应先在顶板上安装后置埋件，然后将灯具固定在后置埋件上。严禁安装在木楔、木砖上。是什么意思？

12. Weight when the chandeliers at 3kg and over time, you should first back embedded parts installed on the roof, and seated in the rear on the buried parts of lamps. Installed on a wooden wedge, wood bricks is strictly prohibited.