On Mon, 25 Oct 2004 06:06:22 GMT, patriarch
wrote:

Or, also safely, install the factory Unisaw insert, and double stick tape
the zero clearance plate over it. Then clamp the sandwich to the table top
with a tubafor and a couple of clamps, and raise your blade slowly through
the zero clearance plate.

I use these methods all of the time with shop-made zero clearance inserts.
I'm really nervous about the method Steve recommends...

You may want to google the archives regarding these inserts. There was a
good thread, humourous and informative, on making these yourself, sometime
in the last year or so. Originated by Unisaw A100, I believe.

Patriarch

I've never had one that I couldn't lower the blade enough to miss, but
if I did...
I might try the partially installed insert thing like the answer that
scared everyone, but with your 2x4 method... at least my hand(s) would
be a few feet from the blade in case the insert bound or something..