While climbing a ladder or vine, the A button says "Down". It is possible to keep this state while not being on a ladder, which can cause some unusual effects.
-The Lens of Truth is the only usable item in this state. The B button and C buttons are dimmed otherwise.
-Weird camera which spins if you hold down on the control stick.
-Jumping off a ledge, climbing anything, receiving damage, or entering a new area will cancel Down A.
-Down A is useful for a method of Restricted Items.
If you climb a ladder or vine with your shield out then shield damage, you will be pushed off but keep the "Down A" state active. This is most easily accomplished by having your sword in your hand, then holding Z and R, then climbing a ladder.
While holding onto a climbable ledge, the A button says "Down". There are certain ways to keep this state after letting go of the ledge.
-Ledge Down A disables all C buttons if the B button is not dimmed.
-If your B button is dimmed, which happens in some indoor areas, or if you have a blank B button, the usability of C buttons will not be updated while you are hanging from a ledge. If you had an undimmed c button when getting Ledge Down A, they will stay usable even if you equip normally unusable items such as the Giant's Mask on them. This is a method of Restricted Items
-If you get Ledge Down A, then equip Lens of Truth to C and climb a ladder, the c button will be enabled. You can then equip other items on that c button and it will remain usable. This is another Restricted Items method.
-Jumping off a ledge, climbing a ledge, receiving damage, or entering a new area will cancel Ledge Down A.