Ceiling keel how big hole reinforcement suitable

Suspended ceiling keel 1200 millimeters or so large hole reinforcement appropriate. Ceiling main keel are used C38 light steel keel, in the ceiling, the spacing range of the main keel control in the 1200 mm or so, the use of matching hanging cabinets for connection, according to the net height of the ceiling of the house, the use of cement nails for the fixing of 25mm * 25mm baking varnish keel.