You simply hammers the note with the side of your pick; extremly rapidly. Take a look at this one (Hope you'll understand it):
tre-T tre-T tre-T
e|--10--(12)--9--(12)--7--(12)--|
B|----------------------------------------------|
G|----------------------------------------------|
D|----------------------------------------------|
A|----------------------------------------------|
E|----------------------------------------------|
Peace Sells... But Who's Buying?