William Brown wrote:

I'm not an electrician, but years ago I was taught to put an
underwriter's knot at the end of the cord when rewiring a lamp
or a plug.

Yep, for strain relief, in case the crd got pulled on, the
knot would (hopefully) keep the wire from ripping right off
of the screw terminals. This was all well and good, when you
had room for them and there was no other method...

I have an extension cord with broken plugs, so I went to our
last independent hardware store here and picked up new plugs
made, naturally, in Mexico.

Somehow I am sensing a bit of a chip on the old shoulder here?
the shoulder that points south??? g

I dutifully tied my underwriter's
knots, but when I tried to get the cover back on the plug it
wouldn't fit; there is no space for the knot. There is a little
notch beside the fastening screw so I fed the wire through that.
Is the knot no longer required,

I think you've answered your own question, sort of. There is no
room for it, so you can't do it. It was never really "required"
but rather just "good workmanship".

The "little notch"? may indeed have an opposite part that
clamps down on it when you tighten down the screws? or is
there maybe a "groove" around it where you could route one
or both of the conductors? (similar to the bottom of most
modern phones, where you can "lock in" the wall cord by
bending it around some posts in a channel). It's my semi-
educated (I can't see it from here, sorry) guess that maybe
the notch is part of the newer version of "strain relief"
2004, se hablo Espanol.

or are these Mexicans trying to burn down my home?

I wouldn't take it personally. ;-)

--
The real Tom Pendergast [ So if you meet me, have some courtesy,
aka I-zheet M'drurz [ have some sympathy, and some taste.
Accept no substitutes! [ Use all your well-learned politesse,
$1 to Mick for the .sig ---[ or I'll lay your soul to waste.