Ft. is a written short form of fort, a strong military place, often with walls. You almost only meet it in names of towns and army sites, especially in the United States: Ft. Worth, Ft. Lauderdale, Ft. Bragg. On maps, signs, and addresses American writing often keeps the little dot (Ft.); some places now write Fort in full. You do not drop Ft. into a normal sentence the way you use a word — it lives inside a place name. It is not ft (the length) and not FT (the newspaper).