They cut a hole inside that wall, which is how it has got the name hole-in-the-wall, and put a pretty powerful PC into that hole, sort of embedded into the wall so that its monitor was sticking
Hicieron un agujero en esa pared, y por eso se llama "agujero en la pared", y pusimos un PC bastante potente en ese agujero, empotrado en la pared de modo que su pantalla