Hi Michael,

On 8/22/2014 6:26 AM, Michael A. Terrell wrote:

rickman wrote:

And they probably thought they had fixed the problem. All you need to
do is to apply something that is not so easily seen but easily removed
by touch. Then check it after the locks have been used, but before they
have been cleaned.

In a defense plant where you had to empty your pockets to get into
the building?

"Dust" from (unused) toilet paper; finely ground salt/sugar from
the cafeteria; thin film of soap (from bathroom sinks); etc.