I thought the tiles on my bathroom floor were perfectly flat and even on the ground, until I switched off the light and used that damn laser on the Dyson vacuum cleaner.
What greeted me was an uneven landscape of tiles that the naked eye just didn't see.
Same, except with panel floor in our bedroom. Moved the bedframe and some cabinets around, suddenly the bed is really wobbly. Couldn't see why until I took my laser level and started sweeping the floor with the "red X" at a low angle, like it was sci-fi scanner.
That laser level actually revealed plenty of places around the apartment I dare not look at anymore, lest I get annoyed at the contractors... and the original builders of the block.
What greeted me was an uneven landscape of tiles that the naked eye just didn't see.