I checked all the dictionaries listed in Wordnikfor spilin, and all definitions related to plugs used for various purposes. For reference, elsewhere in Wordnik, see sny, it is implied that spiling represents the sheer of a ships hull. This is definitely an error. Dictionary.com did use the word "spoil" to describe "Spiling". While I have never been able to connect "spoil" as a source word for spile, it at least provides a good visual for what happens to a board that has been spiled, and then gotten out in a shape that will fit on the hull as required. Spiling is a process that allows one to transfer shape information from the hull to a board via a batten. The secret to using a batten for this purpose follows understanding that the batten anticipates the sny that the newly gotten out plank will experience when the plank is hung on the hull. These terms have been in use in the construction of wooden hulls since before 1711.