How did you ensure that each block was sanded parallel to the front surface?

I laid all the tiles top down on my working surface, put some legos around them and proceeded to sand them - my sanding machine is shaped like a small ironing maching, with a pointed wedge to get into corners.  I sanded them until they looked flat to me.  Not the most scientific of methods perhaps, but I am happy with the "flatness" of the result.  If wiping the blocks would solve my glueing problem next time around, the whole process is workable for me.


Molds owned: 85, 88, 204, 265, 266, 267, 268, 276, 277, 278, 279, 280, 285, 295, 302, 325, 326