Trapdoors open when the block next to them gets broken, placed, replaced or modified.
But you can use this bug to create a Trappdoor Game!
(See second attachment!)
MCPE-8500
Trapdoor opens when the block next to one gets modified.
Resolved
Duplicate
0
(Unassigned)
Unconfirmed
Tablet - Android - Samsung Galaxy Tab 4 Nook
4.4.2
0.11.0 Beta 1
Retrieved
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This issue was reported previously as MCPE-2884; comment your experience there!