For some the phrase "put a mark next to one candidate" is open to interpretation.
Especially to one voter who drew a penis on their ballot slip - only for the vote to count.
Returning Conservative MP Glyn Davies held onto the Montgomeryshire constituency in mid Wales after getting 45% of the voters.
But the 71-year-old said the best part of his election night was the spoiled ballot paper.
Mr Davies wrote on his Facebook page: "One voter decided to draw a detailed representation of a penis instead of a cross in my box on one ballot paper.
"Amazingly, because it was neatly drawn within the confines of the box the returning officer deemed it a valid vote.
"I'm not sure the artist meant it to count, but I am grateful. If I knew who it was, I would like to thank him (or her) personally."