A hole in the wrong place, plugged with the bit that was drilled out plus some other material. In other words: A mistake, Botch or or **** up!
I don;t think that I'm alone in admitting that I've been there and more than once too. I seem to be incapable of remembering lesons, like measure twice cut once etc.Time to admit I made a big mistake. I was drilling a hole, for the new fridge unit I am fitting, from the cool box into the sail locker. I checked all my measurements and drilled a 6 mm hole to check I was in the correct place. Unfortunately the drill was not long enought to go through the glassfibre, the insulation and plywood bulkhead. So I was forced to drill using a core bit to get the drill further into the plywood. Even then I did not get through into the sail locker. Then I moved the drill further out in the chuck and it finally appeared in the sail locker. With all this faffing, I forgot about the painted conduit the drill had just come through, and I used the hole saw from the sail locker. Oh sh*t, I realised I had cut into multiple cabies. Two 2 core ones were cut completely through, but 3 others were still just attached. There were also two 3 core cables that were damaged but still connected. Three other cables were untouched. The two severed cables I am sure are lighting cables running on the same circuit, so do not matter if they were reversed, but just in case they have been marked with coloured electrical tape so I know which may need switching. Luckily there was sufficient slack that I managed to join all of the cables with chocolate box. The damaged conduit has been removed and two pieces of slightly larger conduit are now fitted to hide the cable joints.
So I was 1½" low on my measurement. It was impossible to find a simple way to get it exactly in the right position. The curved line in the left hand corner of the photo is the gas pipe, so I missed that. I have posted this as a lesson that mistakes are easy to make and I should have been more thorough checking once the hole appeared in the sail locker.