Carrying a wood saw without having its blade somehow covered is an accident waiting to happen.
You can construct a simple sleeve for it out of old newspapers.
Step 1: Materials
For the sleeve you only need a couple pages of old newspapers and duct tape.
Step 2: Construction
The construction is really simple.
Take some pages from the newspapers (5 - 6 are enough) and fold them around the blade like an envelope.
Then fold the end of the envelope towards the handle of the blade.
Seal the openings with duct tape.