Grinding is the act of balancing on a Rail and then moving down such Rails at high speeds. While using this technique, the practitioners grind with their feet on the Rails.
In gameplay, grinding is used by the player to move down Rails. By doing this, the playable characters can gain more speed/momentum while grinding. Through grinding, the player can also take shortcuts or obligatory paths made up of Rails through the levels. Grinding is typically as fast as or faster than running. Sometimes, while grinding, the player can also pull off special actions.
To start grinding in gameplay, all the player has to do is touch a Rail.
Sonic Boom: Shattered Crystal
In Sonic Boom: Shattered Crystal, the grinding maneuver is available to all four playable characters in the game. In addition, Shadow will use the grinding maneuver during the race against him in Shadow Canyons.
When grinding in gameplay, the playable characters will be moving at a constant, medium-rate speed, both when going up and down slopes on the Rails.
Sonic Dash 2: Sonic Boom
In Sonic Dash 2: Sonic Boom, the grinding maneuver can be pulled off by all the playable characters in the game.
In gameplay, grinding allows the playable characters to move noticeably faster than when running. Also, while grinding, the player can make the playable characters jump between parallel between parallel Rails by swiping their finger across the screen towards the Rail they want to switch to.
Sonic Boom: Fire & Ice
In Sonic Boom: Fire & Ice, all the five main playable characters in the game and all the Bot Racers are capable of grinding. In gameplay, grinding works exactly like it did in Sonic Boom: Shattered Crystal.