So here's a knot that may very well prove to be stronger than the girth hitch for joining slings. Unlike the girth hitch, which stresses the two runners asymmetrically (the girthing runner loses about 30% of its strength), the climer sling hitch is symmetrical and strong.

Step #1. Wrap the first sling (A1) twice around your hand to form a double loop.	Step #2. Pass the second sling (B) through the double loop of the first sling (A1)
Step #3. Now form another double loop, this time on the second sling (B).	Step #4. Pass the other end (A2) of the first sling through the double loop of the second sling (B)

Step #5.Tighten the knot carefully, working out the kinks so that it looks like the picture shown below. Extra folds or twists weaken the knot.