Green’s Dictionary of Slang

hole in the wall adj.

[hole in the wall n. (4)]

(orig. US) second-class, inferior.

[US]O.O. McIntyre New York Day by Day 8 Mar. [synd. col.] A little hole in the wall delicatessen on Avenue A.
[US]W.R. Burnett Asphalt Jungle in Four Novels (1984) 237: They passed hole-in-the-wall bars, Chinese laundries, poolrooms with a few loafers in front.
[UK]I, Mobster 45: I cornered a rock-headed Neapolitan that had been starving to death in his hole-in-the-wall grocery in our block for twenty years.
[UK]V. McDermid Insidious Intent (2018) 101: ‘It was bought in a hole-in-the-wall shop in Dudley’.