How to implement the same header on 2 different wp themes?

Hi all. The question is, the site on wordpress, it uses two threads. One of them is implemented entirely in header, now it should somehow connect to the second.Please tell me how can I do that?
March 23rd 20 at 18:42
2 answers
March 23rd 20 at 18:44
Realize also, as is done on the 1st topic
March 23rd 20 at 18:46
If you want to avoid duplicated code — implement the cap in a plug-in.

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