[] , [] , [^] , []Alternative of real thing / Wiper of bus(GC World : Sample ,Typical examples of GC)
This is a wiper of bus.
Let's move points.
What movement do you find?
Why does such movement occur?


Actual photograph
When shutting

A little opened

Opened widely

Looking from inside

Expansion a little

Forum of Geometric Constructor by Y.Iijima