Vintage flat head drive screw? Wood helical drive screws? I’m not sure what to call these. Regardless file these under “Bad Ideas.” They are slotted but the slot is enclosed, not open, so they require a screw driver that is an exact fit. To make matters worse, they have a shallow slot. They also have an oblique angled spiral shank so are difficult to unscrew. Most often we see these securing spiral or tube balances to the tops of jambs. But sometimes we see these fastening pulleys to jambs, and even weight chamber access doors. Regardless, they sure are irritating and as often as not require a vise grip, or even a pry bar to remove. In retrofit situations, whenever possible, we’re replacing these with regular vintage slotted screws.