About to start tiling my shower room. (It's been properly boarded out with "Jackoboard" insulated backer board - dot and dab on masonry, with the specified washers and masonry screws). Looking at the wall tiles we bought, I noticed that the edges are not square through the thickness of the tile but slightly tapered and wider at the back than the front (Presumably so the tiles can be removed from the mold when made). In fact when the tiles are butted up there is a gap of about 1mm along the front faces with the back faces touching. So if I use tile spacers (I would like a 3mm grout width), depending on where the tile spacer "sits" within the thickness of the tile, I will get different spacings (up to 1mm) at the front. Q1: How important is it therefore to put all the spacers at the same depth? Q2: What are the best spacers to use? (I have seen some with all sorts of flashing from the moulding still in place and others which are perforated and change width if you squeeze them!). Thanks for any replies or comments.