Stormin Mormon wrote:
I've been asked to anchor aluminum threshold
for commercial doors. About six inches wide, and
runs the width of two 36 inch steel doors. One
half of the threshold is loose, and needs maybe
four or so anchors.

Some how, I remember some blue anchors that look
a bit like drywall screws, but have really aggressive
threads. Anyone know what I need for the job?

Where to find these? Lowe's? Need flat head, so as
not to be a trip hazard. Can't have hex heads.

I haven't read all of the other replies yet, so maybe someone already
mentioned this....

But, have you considered just gluing the threshold down using this?:
http://www.loctiteproducts.com/p/pg_...-Cartridge.htm .