Robert,
The washer is most likely "parallel ground" so that the top and bottom faces are parallel to each other. This distributes the nut's force evenly.
John
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.