When building the Ho railraod model Blast Furnace from Walthers. It is hard to glue the 4 small walls that make the brick pilons under the building and keeping them square and aligned at the same time.
With this jig you glue 2 together then turn the jig and add the 3rd wall, turn again and add the 4th. It will all be square and even.
The author hasn't provided the model origin yet.