Canal Du Midi Secret System of Bicycle Directional Signs
The towpath on which you cycle follows the Canal Du Midi. But sometimes you need to change banks, and that is not always very clear. There is not an official system of signs to help guide you.
At times you will continue straight only to find out a few hundred meters down the road that you have reached a dead end. At that point you can try to dismount your bike and try to proceed by foot in the hope of reaching a decent path again or simply turn around and go back to the first bridge to cross over to the other bank.
At other times you can in fact cycle on either the left or right bank of the Canal Du Midi, but such sections are rare.
But there is a system of very small signs that are posted all along the Canal Du Midi from Sete to Toulouse! These are small stickers put up by different bike tour companies. You have to pay close attention to see them though. And there are different colors and different symbols used by different bike tour companies.
The fact that there are stickers from many different companies is a good thing. Because sometimes you will have 4 stickers pointing in one direction, and a 5th sticker pointing into a different direction. You can bet that that 5th sticker is pointing away from the Canal Du Midi, and thus most likely pointing to a nearby Bed and Breakfast or hotel that that particular bike tour company uses. Thus you should ignore that 5th sticker, and instead follow the direction of the other 4 stickers.

Follow the direction the MAJORITY of the stickers point to. The Blue sticker probably points to a nearby Bed and Breakfast or hotel.

Sometimes the lock keepers themselves have put up signs, probably because they got tired of always having to answer the same question. Here an example at Ecluse de Puicheric.

Here another example where all arrows point in the same direction, this time at Tunnel de Malpas.
Canal Du Midi: Signs along the way
Pictured below is a complete collection of signs you will see along the entire Canal Du Midi, from Toulouse to Sete. Click on the pictures to enlarge them. These are all taken in 2017. Also, remember that each lock has its name written on it.