Slot Vented Screws

In the cross sectional picture above the red area represents material removed by cutting a narrow venting slot into the screw to allow the gas pocket trapped behind the screw to be pumped out. Slot-Vented, often refered to as 'thread-vented', also allows the gas trapped within the screws threads to be vented which center venting cannot reach.

You can see the long narrow venting slot extending from the threaded end into the base of the head of the Redivac© socket head cap screw pictured above.