Ticketbooth has a Box Office feature where the organiser can process door tickets paid by either cash or card.
Sale of door tickets depend per event, the event may or may not sell door tickets. Most of the time, door sales are stated through the event’s ticketing page, event website or Facebook page.
If you cannot find the information regarding door sales, it’s advisable to contact the organiser directly.
If you plan on purchasing door tickets, it’s strongly recommendeded for you to arrive at the venue at least 2 hours before the event starts.