You must use either a 5" metal wrapped edge or full steel channel.
The 20 minute device was discontinued in 2013 - templates are still out there for the discontinued 20 minute devices for anyone that has those old devices, but Allegion does not make them anymore.
If using a 5" metal wrapped edge, use W-1242 to prepare the wood door, and use W-1250 to prepare the metal wrap.
If using steel channel construction, use W-1250.
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