Take control of an infantry soldier
Select your primary weapon and use the 'adjust stance' keys to move your avatar up and down, left and right. Notice your avatar leans left and right and raises/lowers its height incrementally.
Select binoculars and attempt to use the 'adjust stance' keys to move your avatar up and down, left and right. Notice your avatar does not respond to adjust stance keys.
Go prone while holding binoculars and press the 'evasive left' or evasive right' keys. Notice your avatar does not roll while holding binoculars.