pilot hole

plural pilot holes · alternative pilot-hole

1. A narrow hole drilled or punched into a surface, to facilitate the insertion of a wider screw, nail, drill bit, or other boring tool.

   1970, Andy Lang, "Right Nail Hits the Spot," St Petersburg Times, 25 Oct., p. 5-G (retrieved 7 Dec. 2008), Nothing prevents splitting the wood as much as first driving a pilot hole, especially for hard wood.

   1 more example

   During the sinking of the last 150 feet, a pilot-hole was kept in advance, so as to prevent any unforeseen inrush of water.

   1908, W. McKay, “The Boultham Well at Lincoln,”, in Transactions of the Manchester Geological and Mining Society, volume 30, page 29