What does 'deep brakes' mean?

[CoolBeans 11]

Is it when I hold toggles all the way down, around my knees?

Also, especially in base community, I know that some people adjust brakes to be at 'deep brakes' level right after canopy inflation. What happens when they pull the already 'deep brakes' all the way down to knees level?

Edited April 24, 2019 by CoolBeans

[pchapman 279]

1 hour ago, CoolBeans said:

What does it mean when skydivers fly in 'deep brakes', especially for accuracy landing? My understanding is that any skydiver can fly normally or fly in 'deep brakes'. 

'Deep' is relative to whatever the stall point of the canopy is. Which could be with toggles past full arm extension, or chest level, or whatever applies to you and your arms in that particular harness with that particular canopy. So you can fly with no brakes, shallow brakes, moderate brakes (or medium or whatever term you want), or deep brakes. There's no specific definition (eg, "75-99% of the usable brake range before the first pre-stall rocking"). It's just "a lot of brake, getting closer to the point where you would stall the canopy or have arms fully extended".
In deep brakes the canopy will fly a steeper line towards the ground, a steeper descent. The canopy might be dropping vertically faster than in moderate brakes, although possible less than when in no brakes, if it is a ground hungry canopy with a high descent rate in normal flight. 
It is easier to hit a target on the ground when coming down steeply, rather than skimming by at a shallow angle. Deep brakes is good for that. If too deep, you are getting closer to a stall, and thus susceptible to added danger from turbulence or accidentally stalling the canopy. You also won't have much energy left in the canopy for a flare, which isn't a big issue if doing accuracy with a big canopy onto a soft tuffet. If you do need to descend steeply (e.g., landing into a small field surrounded by trees), but would hit the ground too hard without much flare, you might need to have the room to pick up some speed again (out of deep brakes) before doing a flare with more effect.
You might also fly in deep brakes when learning about and practicing approaches to stalls and doing stalls, while up high.
Flying in deep brakes is therefore something with some added risk if not done appropriately, and not generally needed for normal flying and landing (excluding the dynamic activity of the flare), but is useful in specific situations.

[Jyadz 9]

18 minutes ago, CoolBeans said:

Is it when I hold toggles all the way down, around my knees?

Also, especially in base community, I know that some people adjust brakes to be at 'deep brakes' level right after canopy inflation. What happens when they pull the already 'deep brakes' all the way down to knees level?

Deep brakes is when (mainly in BASE) you set your brakes deeper so that when your canopy opens its flying forward at a very slow speed to prevent object strike in the case of an off heading. This is brake setting that comes with your BASE canopy or some people will set up custom deep brakes. Pulling your brakes to knee level is the flare and is not deep breaks. Deep breaks still let the canopy fly forward just slower while the flare is about stalling your canopy. If your in deep breaks and you pull the breaks to your knees (flaring) your just going to have less flare power vs flaring from full flight.  

 

[CoolBeans 11]

What does it mean when skydivers fly in 'deep brakes', especially for accuracy landing? My understanding is that any skydiver can fly normally or fly in 'deep brakes'.