A winding hole (/ˈwɪndɪŋ/) is a widened area of a canal (usually in the United Kingdom), used for turning a canal boat such as a narrowboat.
The word is correctly pronounced with a short "i" to rhyme with "tinned", rather than to rhyme with "finding". It has been suggested that the word derives from the practice of using the prevailing wind to assist with the turn, but no verifiable reference has been quoted for this suggestion. However, nowadays, both pronunciations are in use. In German the term for turning a vehicle is "wenden"; this suggests Germanic origins of the pronunciation.
Because the width of a canal channel (about thirty to forty feet) is less than the length of a full-size canal boat it is not usually possible to turn a boat in the canal. Winding holes are typically indentations in the off-side (non-towpath side) of the canal, allowing sufficient space to turn the boat.
One unverified suggestion for the derivation of the name winding hole comes from the fact that the winding hole is on the off-side of the canal. When horses were used to pull the boats, it was not possible for them to assist with the turning of the boat, due to being on the wrong side of the canal. As a result, it was considered favourable to use the wind to assist in turning the boat, to reduce the amount of human power needed.