Gates are simple structures that obstruct progression through the enemy Forts. Gates cannot be seen or passed though by enemies, but can be freely passed through by allies. Characters can attack enemy Gates to destroy them. Gates do not have any Abilities or attacks, but are usually placed directly between two Towers.
While their most crucial feature is to block enemy movement, Gates also serve to largely prevent line of sight on enemy targets behind them. This only affects enemies on the outside of the Gate - enemies on the inside (and allies on either side) are able to see through the Gates without obstruction. This makes them very useful for defending players to pop in and out of, and an excellent option for retreating from the enemy fire.
While enemy players cannot pass through Gates, special Abilities such as Overpower can allow them to slip over or past them. In most cases this is to the player's disadvantage, as they will now be vulnerable to attack by advancing Minions as well as Heroes and Towers on the other side of the Gate. Crucially, they will be unable to pass back through the Gate (unless another such Ability is used), trapping them within the enemy Fort.