Page 126 - Nate Fitch, Ron Funderburke "Climbing Knots"

Traditional Mule Knot on a Plate/
Aperture/Tuber Belay Device

Traditionally the mule knot has been tied in this
configuration and backed up with an overhand on
a bight. This method avoids using the spine of the
attachment carabiner. Some find the traditional method
cumbersome to tie, difficult to reduce in a precise
manner, or difficult to maintain the brake strand/avoid
slippage. An HMS or pear-shaped locking carabiner,
while still recommended, is not required for this
application. This may be the best indication of when to
use this version.

Traditionally the mule knot
has been tied such that all the
tying is done above the belay
device after an initial pass back
through the carabiner.

Knots Conspicuously Missing from This Book 113