Suppose you're deep-drifting a jig for big-river walleyes. You can feel sharp, abrupt ticks on the line when the lure bounces off rocks. As the jig drifts into some weeds, you feel a slow, mushy pull while it slows and stops. After you snap the rod tip to free the jig, the drift continues. Then you feel a quick tap-tap in the line, softer than a rock but not mushy like the weeds. It's a walleye, and you set the hook.