DECKED drain plugs are compatible with full-size SHORT (64.5" in length) systems and midsize systems. They don't work that well with Standard (75.25" in length) systems, unless you're Kareem Abdul-Jabbar, as you likely won't be able to reach them. The drain plugs are meant to be placed in the cabside/driver end of DECKED drawers. You can place the drain plug in the tailgate end of the drawer, but it's not recommended as it may cause it to drag on your tailgate when the drawer is loaded.
Pickup truck beds naturally drain toward the cab, not the tailgate. That is why our drain plugs are cabside. However, if you prefer, you can drill a small hole in the tailgate end of the drawers (there is a dimple to get your hole started) to create a simpler solution (but that will also create an opportunity for water intrusion).