Boiled linseed oil reacts with air to harden (and can react with air in a soaked rag vigorously enough to spontaneously ignite). Thick sections will never harden. To apply boiled linseed oil, apply a coat and let it cure for a day or two. Then apply a coat once day for a week for a decent finish. Then apply once a week for a month for a better finish. Then once a month for a year for the best finish. Then once a year for the rest of your life to maintain that finish.
It can be used on doors, decks and fences for water resistance, but it has no UV resistance so it doesn't hold up well in strong sun light. It can be used on dirt floors to seal and harden the soil.
It was used by the US military to seal gunstocks for much of the last century. In an effort to give idle solders something to do, they were given little bottles of the stuff and encouraged to use it to maintain their wood stocked rifles. Given enough coats the old rifles stocks became beautiful furniture.
It is a good finish to use on a working knife, but you need to understand how to apply it. It goes on thin, soaks in for a few minutes, and is mostly wiped off. Thick wet areas will stay soft and sticky forever. Repeat.
Unboiled linseed oil dries very very slowly. Boiled linseed oil cures fast. Modern "boiled" linseed oil is not boiled, it has additives that accomplish the same thing. Those additives are not safe to eat, so it should not be used on children's toys or cutting blocks.