ㄴ 분 알다

those who have done it know

분 is the respectful word for a person, so -ㄴ 분 is 'those of you who have done this'. All four lines here are the same move by a presenter: anyone who fired a rifle in the army will know, anyone who has been to that intersection will know, anyone who has worn one will know. 알겠지만 — you'll know, but for everyone else — lets the speaker explain something without talking down to the people who already get it.

Register: audience-facing, polite