My levellers were loose in a box with no instructions - but unsurprisingly I found
3) Before the cement or tile glue has completely dried up (usually no more than 6 hours),
tighten the adjusting cover in the opposite direction, then rotate the T-pin 90 degrees
so that the T-pin turns to a zigzag parallel to the tile, and remove the leveler;
Tricky when you don't live on site!