Many messenger bags don't come with a third-leg stabilizing strap, which comes in handy when riding a bike or doing anything active. Here's how to add your own!
Step 1: The strap
The strap I used came from a sleeping bag I think. It's been kicking around for a while because I knew it would come in handy. You should be able to pick one up at camping store or sporting goods store. Nylon is good and the stronger the clip the better.
Wrap the pronged end around your messenger bag's strap then cut it leaving a good 4 inch tail. In order to keep the freshly cut end from fraying it's good to burn it. I used a "hot knife" which is the right tool for the job but scissors and a lighter work fine too.
Step 2: Sew the pronged end
The last time I sewed was in 7th grade home economics, so don't use my terrible job as an example.
Wrap the pronged end around the messenger bag strap and sew it to itself. The stronger the better, so many passes with the sewing machine is good.
Step 3: Size the second part of the strap
Put on the messenger bag and size up how long you want the new third-leg to be. The length of the third-leg will depend on how full your bag is, so keep that in mind when you are determining how long to make it. The strap I used is adjustable which is sweet for varying bag fullness.
Step 4: Sew the second part of the new strap.
Sew this the same way as the first side, and not as shoddy as me. The leftover piece of tail can be cut off and burned.