When I'm out shopping, I tend to forget that, whatever I buy, I have to carry home - on the bus if I'm lucky, by cab if I'm very lucky [ a 2-hour wait for a cab isn't that unusual] or on foot [about a 45-miute walk].
I came up with this out sheer necessity, having over-shopped and no buses or cabs for the foreseeable future.
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Step 1: The Problem:
This is how I usually got my shopping and myself home - and, with the stick, it meant that I only had one hand to carry the bags in. These bags are rather annoying; if carried in the hand the bags tend to bump the ground, so one has to lean a bit, or sling them on one's forearm, to keep them off the ground.
Step 2: The Solution:
One day it happened to be a bit chilly, so I had a scarf with me.
I was struggling with the bags as usual ... and then came the lightbulb-over-the-head moment. I put the scarf through the handles and tied it in an ordinary reef knot [aka square knot].
Step 3: The Result:
And hey presto, hands-free. It still weighs the same, of course, but one's shoulder is much better able to take the strain than one's hands - especially if essentially one-handed!
This way I can swop them from side to side, to give each shoulder a rest.
I've carried four such bags home on occasion, all fully loaded. Not much fun, but a whole lot better than struggling with them in my hand.
Step 4: Some Notes:
 It can be a pain when the material gets crumpled and stretched, as is bound to happen; it rolls and folds and they can dig in. But still less of a pain than hand-carrying.
 The weight needs to be fairly evenly distributed front and back, otherwise there'll be slippage. But one can always hoik them back into place.
 This obviously wouldn't work on all scarf materials! The label on this scarf says "100% Polyester" - just as well I didn't wear my stretchy woolly one or I'd never have thought to try this. Now this scarf goes in my bag whenever I go shopping, in case of need.