Those pieces are simple little bits of wood to put in the inner corner of dock intersections or the corners between docks and buildings. Without them, your people are likely to try and jump across the corner and take a step on the bottom of the lake.
The corner pieces are free to build and several of them can be placed over the same square.
Select a corner piece and click on the Remove button in the info window if you wish to get rid of it.
- Construction Requirements: free