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Used in plywood boat building as one example.

Spent a lot of time dialing in the jig. Setting the saw blade to 7.5 degrees wasn't even close. Had to add a 3/4" plywood underneath the cuts for support because the 1/4" ply was bending at 3 1/2". This caused the blade guard to be removed, but no worries, the blade was buried in the ply. Many cuts later it dialed in fo a perfect scarf at 2 1/8". Now ready to build😎

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I bought the West System scraffer after trying to use a hand plane to scraf joints in plywood. I just wasn't happy with the results I was getting using the hand plane. After a few practice runs using the West Systems Scraffer I was able to make nice clean, consistent scrafs. You do have to carefully mount and clamp the plywood to a sturdy work surface or table as described in the owner's manual. Once setup it takes less than a minute to make a quality scraf cut. The thing that gave me the most trouble with the West System scraffer was mounting it to my skill saw. It requires drilling five holes into the saw's base plate. I found clamping and drilling the new mounting holes difficult and tedious.

I used this to scarf 3/8" plywood to make 2'x16' pieces for planking. Once set up it was extremely easy to use. It was quick. And, most importantly it made a PERFECT scarf that required no additional work. I tell my friends it is the best tool I have for it's intended purpose.

Finished Plywood Scarfs

Pre drilled holes in scarfing unit did not match the base plate of the Milwaukee circular saw making the unit fussy to install. Scarf cuts seem to be reasonably accurate though the addition of the guide makes the assembly very heavy. New users should practice before making cuts on expensive marine grade plywood. Also, a carbide tipped finish quality blade should be used.

The setup instructions may be in error. The recommended blade angle and clearance were not eve close (I needed 0 degrees and near 0 clearance for an 8:1 scarf.), but after some experimentation, I got near perfect results.

This tool or jig really simplifies cutting a tricky joint. All you need is a standard skill saw and this unit and you are good to go. A long scarf makes for a super strong glued joint.