This is a simple solution for a whiteboard dry-erase marker. Like others, I grew tired of horizontal trays - you bump it and everything falls to the floor, and when you try to use the marker it constantly streaks even if there is plenty of ink inside. They tell you to store them horizontally, but that spreads the ink across the entire marker. This can be a good thing, but usually ends up with me throwing the marker away early since I hate the streaks with a burning passion. 

This marker holder is designed to fit a Quartet brand whiteboard, but I'm sure it could work on others as the design is quite simple. The orientation holds the marker vertically, making the ink stay at the tip for those clean, dark lines. Design also has the label “Ink Stick” because “Marker Holder” has a lot of characters and sounds boring to me.

This mod attaches on the right side of the board with the label facing forward and the large hole facing up. Hook the clips in the back first, then turn it towards the whiteboard until the front clips click into place. It fits snug, and can be adjusted or removed by pulling the front clips back.