Most gamers keep their movement cards in their hand, selecting them by searching in the deck when planning.
A card holder helps viewing the available cards of each deck, before planning.
It is easier for newcommers, but I also use it for myself and my game partners as we find them more practical in order to find easily the cards needed during the game.
At the end of the game, the cards are already classified, for the next game.
The first pictures show card holders made with old audio tape boxes.
The fourth picture shows an official card holder included in the game Ticker to ride - Asia expansion (6 holders in a box set).
The cards holder shown on the four last pictures come from the game Rummykub and are normally designed to hold dominoes.
They suit for small movement cards, but adding a thick adhesive rubber (blue lines on picures) on the edge of the 2 supports prevent cards from slipping.
The rubber is neccessary to hold the larger cards of WW2 fastest planes.
The Rummikub holder is stable and holds a full deck without being cumbersome.
It creates a "cockpit area".
(4 holders in a box set)