Locking Dock Icons

This is my first post here, but I was recommended by someone else to post this question here. I have some users in a manufacturing environment (building Fords and Mercuries) with Mac minis that use a touch screen and barcode scanner. Sometimes the users accidentally drag the icons out of the dock and they disappear until we bring them back. I simply would like to find a way to make the dock now allow this removal. Do you have any ideas of how this can be done? Thanks!