The gap between the rails is around 7cm, but it varies slightly depending on the bed’s size.If you'd like the gap between the vertical rails to be narrower or wider than 7cm we can do this for an additional fee of £30. Please bare in mind that the instruction manual is written for gaps of 7cm. Please note that if you opt for the rounded opening, it is not possible to make the gap between this opening and the next slat narrower than 7cm.