Always display your boat name and boat index number on both sides of your boat. You can get it painted on, use vinyl stick-on or even have laminated cards displayed inside the windows if they are large enough.
As well as being a legal requirement under the General Canal Bye-Laws 5(1) that the index number is clearly displayed on both sides of your boat (front and rear are not acceptable), it is also a condition of your boat licence. It’s also important that you display your index number and boat name for insurance purposes in the event of an incident and for identification purposes of the boat in an emergency.