Like this
RUNNING THE RACK
this is a grip excercise that sounds pretty easy but if you have a full set of dumbells can hit your grip and forearms pretty hard .
start in front of the db rack faceing the smaller weights at either the 5s or 10s , simply pick up the dbs and hold them for 15 seconds [ dont cheat lol ] the rack them and immediately slide over and pick up the next heaviest pair of dumbells and repeat the process . do this all the way down the dumbell rack as far as you can . it doesnt sound hard but most people will be shot long before they get to the dbs well over 100 #s if they truly hold the weight for at least 15 seconds . if you are more advanced or your gym doesnt have very heavy dumbells simply stretch the time out to 20 or more seconds