what is monofilament?

this is about diagnosing diabetes mellitus:

for foot inspection - monofilament or vibration at great toe

what is monofilament and how is this test done?

this is what I found:

"A quick screening for neuropathy is to verify vibration sense at the great toe. A more practical test is to use the monofilament, which looks like a thick fishing line. The exam is painless to the patient. If he or she can't feel the touch of the monofilament, or only feels it sometimes, then the protection sensation has been lost and the individual is at risk for foot ulcers. I refer you to the Lower Extremity Amputation Prevention (LEAP) websites below for more information on the monofilament and how to order some. The usual medical supply companies will also have them available"