Card

Use large cards

By using a large format (letter, A4), the lost of a card will be quite impossible, and errors during execution (card not removed or not in/on a box) will become obvious and then corrected immediately. This is the best solution to garantee the rigourous use of this system.

You can put a large card vertical in a box, displaying all the necessary information. Easy to be seen, this card cannot be forgotten by all.

Use the good KANBAN unit

An other common mistake is to think that using a small KANBAN unit will decrease the inventory. For example:

you consume 1000 components per day of a reference;
its batch size is 500;
its box size 10;
its pallet quantity 100.

Using a KANBAN card per box is not necessary. You may better choose the pallet as the KANBAN unit. You will have less cards to manage (and loose) without impacting your average inventory level.

Use Colours and Icons

Having a KANBAN storage area well organized and easy to audit (parts at the right place, each KANBAN unit with a KANBAN card) is key to insure a robust process. Nevertheless, it is difficult to read a 6 to 10 digits reference without doing an error once in a while. When you have to check if all boxes in a storage area have the same reference, this can be quite long.
If you have on cards specific color for each reference, this process can be faster. Unfortunately your eyes cannot quickly distinguish a lot of colors (8/9 max) so this method cannot be used when you have a lot of references.
If you add to the color a little icon (small shape) and you link this couple to a reference, you are multiplying the possibilities without a risk of confusion.

If the number of possibilities is not enough, you can associate 2 icons to the colour. In this case you are going to cover all needs of identification.
Associate a color and an icon to a reference can help you to detect immediately mixed parts in your inventory, in the Batch Building Box or in the Launcher. This is a very amazing visual tool. Auditing a KANBAN area using this technique can reduce the audit time by more than10!
Users find this method easy to use. After a period of time, they will use the associated colour code / icons instead of the reference! So do not change the association without a good communication.

Display just the right information

At least you need to have on your card:

the reference in large black font on white (to facilitate long range reading);
its equivalent colour and icons;
the quantity represented by the card;
the KANBAN family (when you are in the specific case of a multi-levels KANBAN).

You can add to improve the comfort of use:

The designation/description of the product;
The picture of the product (if you have similar products);
The reference of the main components (in this case you need to be sure that the card will be updated when the Bill Of Material of the product will change);
The customer production line if you have a production line feeding multiple production lines and products dedicated to a specific one (in order to organize your KANBAN storage area by customer production line);
The production line if you have a KANBAN storage area shared by multiple production lines (not recommended).

But remember: more you have data on the card, more it will be difficult to read and maintain it!

Use a standard card layout

All KANBAN cards used by a process need to have the same size and layout. A plus is to have the same card layout used for all your processes using KANBAN. This facilitates the cards maintenance and helps the deployment of the KANBAN within your shop floor.