Need help identifying what is this on a apple tree

A friend of mine has an old apple tree that have this outgrowing rug spots on the trunk and some tick branches and would like to know what it is. Is it bad for the tree? If so what do about it. Thanks in advance for helping out!

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Those are burr knots .
Some varieties get them on the underside of scaffold branches.
( I have some on spur type winter banana apple )


Thank you so much @Hillbillyhort I never thought about that because it has so many all over, I only took those pics but they ware way more than those captured on the pics.
I’ll pass the message along

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