I'm quite new to printing graphics. I understand why crop marks are used when printing, and on the face of it, they seem quite straight-forward to use. However, when I went to trim a document I have printed using the crop marks that were added (using Illustrator), I came across an issue that has me confused.
Take the example above. If I was to trim the top of the document, using the two horizontal crop marks, then I would also remove the two vertical crop marks indicating the left and right edges of the final document. As a result, when I go to trim say the left-hand side of the document, there is no crop mark to use as a guide at the top.
My question therefore is: how is a document trimmed using crop marks such that when a cut is made in one direction (eg. horizontally) the crop marks necessary for trimming the document in the other direction (eg. vertically) are not removed? Or is there something else I am missing?