In tic-tac slang, four to one is rouf (four backwards).
Your stake: £1 win
Horse wins: £4 profit
2/3 place: No pay-out
Your stake: £1 e/w (£2 bet)
Horse wins: £5 profit
2/3 place: £2 return (Level on bet)
(Based on a handicap with more than 16 runners, such as the Grand National. The amount and number of each-way payouts varies depending on the size of field and type of race)