Guns are usually instantly fatal and available in the home.

Overdosing is dangerous, but it's less lethal than gunshot.

Falls from high places are dangerous, but it requires the person makes a plan to travel to that location which doesn't fit for the rapid onset nature of many suicide attempts. Death by falls and fracture (these include jumping in front of trains) account for a small number of deaths by suicide. So, people can do it. But they tend not to do it. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsde...