The last workshoes I have bought for several years have a grid or thread design that retaing small pebbles, dirt, shavings, and lots of other junk. It would seem that the manufacturers would have some test for the sole pattern and could provide soles that could be worn from outside to inside without having to take a pick or other to clear the debris out. Using a bristle matt does not dislodge the junk and a pick or similar is needed. I made a pick out of a framing nail with head cut off in a wood handle, but that is only for use at home.