Blast gate for DN50 ceiling mount (german: HT-Rohr)

I modified the original design to be able to attach the gate under the ceiling (eyelets for chains or ropes for operation).
I also modified it so that it can be inserted between existing HT tubes. The coupling contains a normal rubber lip seal.

Materials required:

• 3x M3x16 screws
• 1x M6x20 bolt
  plus nuts and washers
• DN50 lip seal (e.g. https://www.hornbach.de/p/ht-ersatzlippendichtring-dn-50-mm/266502/)
• Two chains/ropes of appropriate length, possibly key rings (or cable ties)