"Danger space" is the hull that can be hit at and above the waterline (upper hull side from the waterline up and the weather deck), though a downward-moving shell can hit the below-deck area sometimes, particularly at a high angle of fall. This puts reserve buoyancy and engine/boiler rooms (most extend up somewhat above the waterline) in direct danger of penetrating hits. This is where an "over" hit in the "shadow" of the ship behind it would be stopped by running into the ship structure (usually limited to the hull in most charts) first, on top of those hits that would run into the hitting space when they hit on the near-side of the hull (hull width) -- shadow + hitting space (hull width from the side) = danger space.
"Hitting space" is that hull horizonal area **at the waterline** that can be hit by the same shell, so it is smaller at closer ranges than the danger space -- this is what would put below-the-waterline gun magazines in danger at the given range. Thus, it is always the hull width against an enemy on your ship's broadside and hull length against an enemy firing over the bow or stern (much larger, so raking fire is not a good thing to be on the receiving end of!). Hitting space is thus a subset of the total danger space. The USS MONITOR, other than the turret and small conning tower, would essentially ALWAYS have the hitting and danger spaces essentially the same, since the hull's weather deck is only a few inches above the waterline.
The 32cm vertical KC n/A side armor (on top of about 2.5cm of Shipbuilding Steel 52 (high tensile steel) hull plating and a 10cm teak cushion; slightly tilted outboard in the bow region) backed up by the 11cm (12cm alongside TIRPITZ magazines, I think) sloped Wh armor deck at 68 degrees from the vertical is more-or-less proof against any shell hitting this pair of plates from the side at any range. Penetrating the belt with an undamaged projectile will cause it to be tilted up somewhat horizontally from its original angle of fall, so that the impact on the sloped deck is usually over 70 degrees, which makes that plate VERY difficult to penetrate with any projectile slowed down by the main belt first. My computations showed nobody could penetrate it, but I did not try every possible gun and shell, so it might be possible at very close range for some gun, but that is unlikely to happen unless BISMARCK/TIRPITZ is already smashed up.
The 14.5cm KC n/A upper hull (on the same backing) starts high enough on the hull that only at an extended range -- and thus lower striking velocity -- would the sloped deck be hit after hitting this thinner belt armor, so this does not give any real improvement on being able to penetrate this sloped region. The 14.5cm upper belt and 8cm Wh near-waterline flat armored deck (11cm/12cm over the magazines for BISMARCK/TIRPITZ, respectively) is also difficult to penetrate, especially as the fuze delay in most shells would stop the shell -- break it mostly into pieces when the filler goes off -- between the two plates in most cases (other than a dud, a defective delay element with an over-long delay, or a Japanese "diving" Type 88/91 AP shell with its super-long fuze delay).
The 5cm Wh weather deck (perhaps 8cm in reinforcing rings around the main barbettes, but I do not have details) spaced about 6.5m above the armored deck gives kind of a thin total deck in purely penetration terms, but the long distance also gives most delay-action fuzes time to destroy the shell prior to hitting the main armor deck when colming in from the side at a shallow angle, so again the chance of penetrating this is not good for a non-Japanese properly-functioning shell. Thus, you have to be firing at a very long range so that the shell is coming down very steeply to allow the distance after hitting the weather deck to get small enough to allow most APC shells to reach the lower armored deck intact in the first place. Note, though, that you get the upper hull smashed up right down to the waterline in the hit region for virtually ALL hull hits even if the main armored deck stops the damage beneath it, so these ships are losing a lot of reserve buoyancy against any hull hit whatsoever to try to protect their lower hull from plunging fire.
Note that firing over BISMARCK/TIRPITZ bow or stern in raking fire eliminates most of this added layered protection (no sloped deck, no thick main belt (just a single vertical transverse bulkhead of reduced thickness), hull plating thin enough in front of the transverse bulkhead armor that the base fuze of most large shells may not be set off until the armor itself is reached, etc.), so BISMARCK/TIRPITZ lower hull is MUCH more vulnerable at any range from the bow or stern. This is somewhat true for most battleships, but the difference is MUCH bigger for these German ships!!