Symbolising the right to a secret vote, it is the thousands of boxes across the country that will hold the key to the nation's future.
Other nations, including some in the third world, have introduced new technology including voting machines, the UK polling system is much the same as more than a century ago when the secret ballot was introduced.
This could take some time...
Some countries will know an election result within minutes of polls closing, but in the UK the mysteries of the black box can take a whole night to count - and sometimes beyond.
Ballot boxes were introduced in 1872, five years after the second "leap in the dark" Reform Act extended the vote to large numbers of working class people.
Before that balloting was open, allowing people at the hustings to see how anyone voted with all the intimidation from candidates' heavies that went with it.
The black metal container now has a rival in a grey plastic version which is lighter to carry from the polling station to the counting centre.
Unzip and count
Also aiding flexibility is the hinged version enabling the box to be folded flat and then erected on site. And there is even a PVC/nylon one that can be unzipped and carried as a flatpack.
Ballot boxes are locked and sealed to ensure they are not tampered with. At least one box must be available for each polling district - of which there are about 80 on average in a parliamentary constituency.
They have to be tamper proof and robust enough to withstand the rigours of their rushed journey from the polling station to the counting hall by car, boat or helicopter.
Most past incidents have been caused by fire - possibly due to nervous voters having a quick smoke while they ponder their crucial decision.