I used to work for an engineering company. On one large project we had installed a 10'' (275mm) cast iron underground water main all around the entire site. High pressure mains like this have 'thrust blocks' installed at every change of direction to essentially stop the main from moving when large quantities of water are suddenly turned through 90 degs.
The thrust block is usually something like a 1m cube of concrete, the elbow on the water main resting on the block.
We had a dead end on the main sealed with a blank flange, ready for any future extension. The blank flange had a thrust block to stop movement.
So testing the main involved filling with water and then using a hand pump increasing the pressure to well above the expected working pressure (probably 300psi/ 20 bar) to check for leaks and movement.
Cue the inspector walking the main checking for leaks etc and eventually he comes to the blank flange. he is not amused to see there is a gap between the flange and the block, he says to his mate:
' Look at this, enough room to get your bloody fingers in.'
And he demonstrates by sticking his hand in. One second before or one second later he would have been fine. The main shifted at exactly the wrong time and he lost two fingers between the bolts on the flange and the thrust block.