The Electoral Commission has stepped into a row over the use of pencils in today's referendum.
Concerns that votes might be erased and changed sparked concern on social media, with #usepens trending on Twitter.
And voters at one North east polling station complained at being provided with pencils to cast their vote.
Malcolm Thompson, who attended the station at at Eppleton Cricket Club said: "There was a bit of a commotion going on.
"People were saying we should not have been provided with pencils because they could be rubbed out.
"They have got a point - I know it seems trivial, but it is an important vote.
"Luckily, I had a pen in my pocket, but not everybody carries a pen about.
"I complained to the staff, who said Sunderland Council provides the pencils and pens might be stolen - but the pencils are attached to the voting booths."
Sixty-eight-year-old Norman Barnfield had been to vote at the polling station in Miers Avenue, Hartlepool, this morning.
"I was just inquiring why, in the polling station, it was pencils instead of pens," he said.
"I said 'It's probably so it can be rubbed out.' I was talking to somebody and she said all the polling stations in the country are using pencils."
"Why are they using pencisl? It has always been pens."
The Electoral Commission told the BBC: "the use of a pen or pencil when completing the ballot paper is not specified in legislation.
"In the UK, pencils are traditionally used for the purposes of marking ballot papers and are made available inside polling stations for voters to use. Having said this, there is nothing to stop a voter from using a pen to mark their vote - there is no legal requirement for ballot papers to be marked with a pencil.
"Pencils have been used partly for historic and partly for practical reasons."
And the Commission's own Twitter feed underlined the point: "Remember – using a pencil to vote in the #EURef is fine. But you can use your own pen if you wish. Just don’t leave it behind!"