Simple. Just equip your Gravity Gun,grab an ideal object,and give your Gravity Gun a jolt,and the object below will fly up,causing you to jump farther.Heavy things,such as dumpsters,heavy metal,and such,will usually not take you as far as lighter thing like barrels,metal plates,boxes,and small furniture.Gravity Jumping starts to get more fun near the end of the game where you get the super-charged Gravity Gun,which can be done to the computer monitors that you can rip off the wall.Not going high enough? There is a way to go even higher with the Gravity Gun! Simply pick up an object,hold it beneath you,and quickly shoot it off! So,what are you waiting for? Pick up that Gravity Gun and start jumping!