exactly 5mm - I love being precise
My new favorite low-tech gadget is these rolling pin sticks that ensure your dough is rolled evenly to a specific thickness. They come in various sizes like 1/8 in, 1/4in, 1/2in, etc. You place them on either side of the dough and roll your rolling pin over them and the dough. No more uneven dough, no more guessing how tall the dough is. These are called Teighölzer in Zurich and I got them at Manor (although I heard they are available at Migros, etc.). You can also use rolling pin rings, basically rubber bands of various thicknesses that slide on the end of your rolling pin.
Also, if you aren't rolling your dough between parchment paper, start today. No more dough sticking to the counter and no more extra counter flour in your dough. Just roll your super sticky dough between the parchment, stick it in the fridge or freezer for awhile. When firm, take it out to cut or manipulate as needed. If your dough has lots of butter - act fast. My sugar cookies and gingerbread dough go from ice cold to practically liquid in under five minutes.
rolling pin sticks also double as a great toy