Hi, believe it or not, whenever I've needed to use screws, I've just selected them from a box containing all different types and sizes, by sight only. When it comes to actually selecting a screw of a specific size from the screwfix catalogue it becomes tricky because I can't hold the thing in my hand. So my question is "how do I interpret the sizes?" For instance I'm looking at this particular wood screw: http://www.screwfix.com/p/turbogold-countersunk-screws-3-x-16mm-pack-of-200/16957 It's describes as 3 x 16mm. Fine, I imagine that 16mm is the length in mm, but is that the length from tip to the top of the screw or just the length of the thread? And what is the 3? Is that 3mm? or some other measurement? And what is it referring to, the width of the top of the screw, the head, or the width of the shaft? So confusing. Please help.