By using the grab power, any creature can try to seize a target bodily and keep it from moving. Although class powers and monster powers are usually more effective than grab at locking a target down, the advantage of grab is that anyone can use it, regardless of class.
GRAB: STANDARD ACTION
Target: You can attempt to grab a creature that is smaller than you, the same size category as you, or
one category larger than you. The creature must be within your melee reach (don’t count extra reach
from a weapon).
Strength Attack: Make a Strength attack vs. Reflex. Do not add any weapon modifiers. You must have at least one hand free to make a grab attempt.
Hit: The enemy is immobilized until it escapes or you end the grab. Your enemy can attempt to escape on its turn.
Sustaining a Grab: You sustain a grab as a minor action. You can end a grab as a free action.
Effects that End a Grab: If you are affected by a condition that prevents you from taking opportunity actions (such as dazed, stunned, surprised, or unconscious), you immediately let go of a grabbed enemy. If you move away from the creature you’re grabbing, you let go and the grab ends. If a pull, a push, or a slide moves you or the creature you’re grabbing out of your reach, the grab ends.
Published in Player's Handbook, page(s) 290, Player's Handbook 3, page(s) 220, Rules Compendium, page(s) 243.