Adding this as food for thought for our recent discussion on how shields work in Pathfinder 2E.
“Why Armor does not have a BT number like the shield?”
Here's my take on that. Angle Matters. Like tanks in WWII, the angles of the armor deflects shells. Shields are mostly flat with the exception of the Kite shield and the Roman Tower shield and soldiers use them to intentionally catch blows and stop the incoming force, while armor (plate for example) is wrapped around our bodies like ellipses and curves with padding underneath.
When we get hit in plate, odds are we move or our get pushed and are not trying to resist the incoming force. Part of the force (slashing and bludgeoning) that does land is reduced. Piercing probably struggles to even hit at the right angle to penetrate half the time.
Check this out.The WW II German Manual for Tankers, Pantherfibel
“One of these supplements folded out to reveal black and white photos of various Allied tanks along with data on each vehicle to aid the crew in recognition. Other supplements showed graphically at what range the Tiger could be penetrated by and in turn itself penetrate enemy armor such as the Sherman or T-34.”
This diagram from the Tiger Tank manual uses a clock and hours (uhr in German) to advise how to turn to maximize deflection. Even using reference to meal times.