The postcards give clues for eight different bands, and have been sent out across Sheffield amid much speculation from festival goers as to who might be playing.
The fronts of the postcards also give hints about the headliners, with an image of Ian Brown on one and the phrase ‘Sheffield and the Bottlemen’ on another.
One person who deciphers the clues will be in line for two free tickets.
The clues are as follows:
“Multiple bee houses
“Living with few difficulties
“Date and marketing association
“Massive natural satellite
“Investigating grey birds
“Bad guys from The Goonies
“A group of eccentric people”
To enter the competition you need to upload a picture of the postcard to Facebook, Twitter or Instagram with you answers filled in and #Tramlines2020 in the post.