"La puerta negra" is "black door" in English. In terms of Los Tigres del Norte's song, it's referencing the door that won't keep the singer away from his love.
"La puerta negra" is one of the most famous vocal contribution of bassist Hernán Hernández (better known as the Tigre with the fabulous Mexi-mullet and streak of gray in his hair), this tale of a girl's parents prohibiting the unrequited love of a couple could've been written by Brian Wilson. Another great opening line: "It's now closed, with three locks/and bolted down, the black door"--positively medieval. Also featuring the most memorable saxophone in Los Tigres' repertoire, a wailing cri de couer.
See La puerta negra song lyrics with English translation at LyricsTranslate.
Check out the 20 Greatest Los Tigres Del Norte Songs of All Time compiled by OCWEEKLY.