The Principality Stadium roof will be open for Wales v England in the Six Nations this Saturday at England's request.
Warren Gatland's Wales host Steve Borthwick's visitors in Cardiff, with the fixture being confirmed to go ahead on Wednesday after the threat of a Welsh player strike was averted.
Wales always prefer for the roof to be closed for their games due to the cauldron-like atmosphere it creates, but the opposition must agree to this for Six Nations fixtures, effectively giving visitors first choice.
It would appear England have vetoed Wales' standard preference to have the roof closed.
The rule over opponents agreeing with Wales' stance does not apply to autumn internationals or other fixtures. Wales get to make that call, but rules for the Six Nations are different.
The roof itself takes 20 minutes to open and costs £2.54 to open each time - all at the press of a button. To close the roof, both sides must travel at exactly the same speed to maintain balance. If the two sides are just a few centimetres out of sync, the system will automatically shut off. The roof is made of 20 shiploads of steel, has 200,000 nuts and bolts and has an opening size of 105m x 80m - compared to the pitch's 120m x 79m dimensions.
POLL: Who will win Wales v England in the Six Nations? Have your say below or right here
READ NEXT:
Warren Gatland gets access to three new Wales players immediately but Rowlands could still be victim
How Wales' Six Nations players voted in crucial last meeting on strike action
Ospreys plan to keep hold of Joe Hawkins as English giants look to swoop
