Disston Screwdiggers fulfil the same function as Screwsinks but the countersinking part can be slid up and down the drill part of the tool.
This means, for example, that a No.8 Screwdigger can be adjusted to predrill for different lengths of No. 8 Screw.
This set contains 1 each No. 6,8,10 & 12 screwdiggers.