A flint-chip razor simile for a beak’s sharpness. Elsewhere in Tarka we encounter birds skewering frogs through the head with their beaks, or otherwise impaling prey.
‘Its beak was sharp as a rock-splinter.’
Source: Henry Williamson, Tarka the Otter: His joyful water-life and death in the two rivers, illus. C.F. Tunnicliffe (Harmondsworth: Puffin Books, 1976 (1927)), p. 197
Photo credit: MabelAmber at pixabay.com