Every printer knows there is a danger of spaces riding up at any time during the press run.  Also it is vitally important when setting hand set type in Hot Stamping type holders or type heads you make sure All spaces are sitting on there feet. In other words they are sitting such that they bottom out at the bottom of the holder.

High spaces exact there toll in damage that mars the appearance of the otherwise well printed job.  In the worst cases the jobs must be scrapped.   The spacers must be kept below the printing surface.