Canal companies guarded their supplies of water, doing their best to ensure that none was lost to other companies at junctions. This was done by inserting a shallow lock (usually rising just a few inches) to separate the waters. A few are still in use (for example Autherley where the Shropshire Union meets the Worcester & Birmingham), but many ceased to operate when the canals came under a single ownership. However, you can still see where they were from the narrowing of the canal and old gate recesses. Our picture shows Nechells Lock where the Birmingham & Warwick Junction Canal (which became part of the Grand Union) met the Birmingham & Fazeley (part of the BCN).