What size screw for Junction box?

The standard screw size for attaching a junction box to a surface is typically 1-1/4 inch to 1-1/2 inch screws, often #8 or #10 in gauge. The exact size may depend on the type of junction box and the mounting surface. Always check the manufacturer's specifications for the specific junction box being used to ensure proper installation. Additionally, use appropriately sized screws to avoid damaging the box or the mounting surface.