Restrictors

Restrictors, or gates as they're sometimes called are the part of an arcade stick that are designed to limit to movement of the stick based on the type of game it will be used for. These are most usually attached to the bottom of the stick where they restrict the movement of the actual shaft of the stick and are most commonly seen on Japanese sticks.

Directions

Restrictors are most often classified based on the number of directions they allow. Of these, there are three main types: 2-way, 4-way and 8-way.

2-Way

2-way restrictors do exactly what they say. They restrict the movement of the shaft to only 2 directions.

4-Way

There are 3 main types of 4-way restrictors: rhombus, plus and circle.

Rhombus restrictors are, for the most part, 8-way square restrictors turned 90 degrees so that the 4 cardinal directions are on the corners of the gate. The advantage of this type of restrictor is that it's easier to hit other directions thanks to the diagonal borders of the gate. However, the problem with this is that it's still somewhat easy to hit 2 adjacent cardinal directions for diagonals (depending on the stick), which can be a problem with some games which do not filter out diagonal commands.

Plus restrictors totally restrict access to diagonals due to the shape of the restrictor. With plus restrictors however, it can be harder to move to the other directions.

Circle restrictors are simply circular gates similar to circular 8-way restrictors.

8-Way

8-way gates are the most common gates seen on most sticks. They allow for movement along 8 directions by letting the actuator hit 2 adjacent cardinal directions at a time for diagonals. There are 3 types of 8-way restrictors: square, octagon and circle.

Square

Square gates are the most common type of 8-way restrictor and are usually the ones found in arcade cabinets (especially those from the Japan).

With square restrictors, the spacing of the engages is usually based toward equal neutral and engage zone sizes (a nine square grid of equal sizes). This means that an equal amount of space is allotted for each direction (including neutral position). The issue most newer players find with square gates is the inability to "ride the gate" that is, use the restrictor as a guide for movement.

Octagon and Circle

Octagonal and circle restrictors on the other hand are much easier to "ride" as the shaft does not get caught in a corner. The problem with these however is that a smaller space is allotted for the diagonals (due to the fact that hitting the diagonals is simply hitting the switches for two adjacent cardinal directions).

No restrictor/Gateless

Some sticks, specifically American, European and Korean sticks are do not have a restrictor. For these sticks, the movement of the shaft is usually restricted by the size and shape of the actuator.