This is an excellent knot for various uses, very strong knot. It's used in mountain climbing. The figure 8 family of knots only lower rope strength by approx...
How to tie the Double Figure 8 on a bight knot.
Double Figure 8 (2 loops)
Double Figure Eight Knot
Double Figure Eights with Banyan
Double Figure-8 Fisherman's Knot
How To Tie A Double Figure 8 Knot
PRI; Double Loop Figure Eight Knot