When the user selects a type B footing (stemwall foundation) a keyway is inserted between the stemwall and footing:
View model here:
https://3dwarehouse.sketchup.com/model.html?id=242c0e7d-db46-43b7-baf6-ce322a842e4e
View model here:
https://3dwarehouse.sketchup.com/model.html?id=242c0e7d-db46-43b7-baf6-ce322a842e4e