What is a wet spot machine used for?

Question

saw this on the side of some kind of railway wagon with a cab at both ends

Answer 1

My mind immediatly went down the gutter on this one, sorry.

In the States we have machines that do a very similar duty to the one described above but they are called undercutters, they remove watersoaked and muddy roadbed gravel, screen the gravel and put it back in the roadbed.

Answer 2

so you know when your girls in the mood for s*x without going anywhere near her first

Answer 3

for mopping up submarine drivers

Answer 4

A Wet Spot Machine is used to repair ballast beds (the gaps where the stone is between the sleepers)

Occasionally the ballast beds in certain areas become waterlogged.  This is called a Wet Spot. A Wet Spot will cause bad ride quality as eventually the ballast in a Wet Spot turns into a greyish mud.

To sort out this problem, the Wet Spot machine is used. It is like a giant vaccum cleaner. It will suck out all of the crud from in, under and around the Wet Spot, and then it will refill the void (hole) that is left with new stone.

There are only a few Wet Spot machines in use in the UK.