The standard slotted head is most effective utilised using a flat screwdriver, while the cross-formed indention is greatest suited to a Phillips screwdriver. A Robertson screw contains a square-shaped indention and needs a matching driver head. The length of those screws may differ, but most drywall screws have flat heads https://screws19641.bloggosite.com/35019423/little-known-facts-about-screws