In rec.woodworking, wrote:
On Fri, 17 Jul 2020 09:32:04 -0700 (PDT), wrote:
I'm looking to cut 3 pass-through mortises (2"x6" long)
on each of eight large pressure-treated square timbers (8"×8" x 8 ft long)
....
Any other suggestions on how to do this easily with hand power tools?
https://tinyurl.com/y4s5z8wh

That looks like an interesting tool, but the longest blade available
appears to be 65mm, which is not long enough to cut through 8" even if
you cut from both sides: 4" is about 102mm.

Elijah
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has no tool suggestions to offer