Following these visual instructions you should be able to do this for your dog. The only caveat is you'll have to tuck in into their collar or hold the strap temporarily.
Just to provide an alternative with rope, which does use cutting, multiple pieces and optional fastening, but is still rather simple and reusable.
How to make a slip knot
Without being there in person you may have to play around with this a bit to figure it out but it's not too difficult.
- Make a slip knot at both ends of 4 ropes or use straps with a looped fastening at both ends.
- While making the loop for last 2 ropes, thread the rope through the loops of one of the first two. This will connect 2 ropes at their loops, making a lens shape. Make sure to leave some slack rope on one of the loops to adjust.
- Using whichever knot you prefer, connect two of the lenses together at a point or use a ring/other type of fastening. Your pet will step through these two "holes" to get the harness on
- Part way up, using whichever knot you prefer, connect a rope running across the two inside parts of the lens, this will go across the front of your pet's chest.
- Finally place another knot, ring or other removal fastening of your choosing at the remaining tips of the 2 lens-shaped "rope rings". This will go behind your pet's back and is where you will attach a leash / rope / etc.
Combining these methods should be possible. If you try post a comment please!
Here is a one-piece version with webbing of my rope method. Note, all mention of right or left legs refers to their front legs. You could probably adapt this for a full body knot though.
- Lift the webbing between your dog's left armpit from behind, so that just enough is in front of them to wrap around toward the back of their neck with a bit extra. Hold the front end of the strap here.
1b. Alternatively, hold one end of the webbing behind the dog's neck, then guide the rest of the rolled up webbing around their neck, forward across their chest and under their left armpit. Same result.
- With the back end of the strap, wrap it over their back also and guide the roll in front of their chest, back behind their right armpit, and up to the back of the neck again.
- You now have two lengths of webbing running in along the front side of your dog's chest and one confused dog. Wrap the webbing around from back to chest behind their left leg and pull it through the front facing strap of their right leg.
- Keep wrapping back toward the spot behind their left leg and pull the strap across the under side of their chest, coming above their back on the right side and wrapping toward the front-facing side on the left side.
- Thread the strap through the front-facing left strap that is across their chest, wrapping toward the under side behind the right leg.
- Finally bring the strap up to the one you're holding at their back and wrap one more time around the underside back up to the back.
- Cinch it all together on top or hook both sides of the webbing to whatever. You're good to go.