Grenade Jump
The grenade jump is a technique of using grenades (usually the frag grenade) to propel the player high into the air. It can be used in combination with some other Jumping Skills and is usable by all classes that have the frag grenade, which is all classes except the Scout class and the special Civilian class.
Performing the jump
The basic jump
The basic premise is easy: drop a frag grenade on the ground and then jump over it when it explodes. The resulting explosion propels you high into the sky. As with anything, practice is needed to get the timing and such down. Of course, as with almost everything in Fortress Forever, slight changes and variations can change the outcome of this jump in many different ways. You can also vary the way you travel; stand a little bit away from the grenade if you want some horizontal distance instead of just going straight up.
Hand-held jump
As an alternative, you don't actually have to drop the grenade in order to do a grenade jump. Just let the timer run its course and jump when it detonates. The timing of this is more difficult than a regular "dropped" jump, but it is more effective and flexible. Running forward and jumping when it detonates will give you horizontal distance.
Notes about grenade jumping
The grenade jump is most useful if you are playing a class that has no other way of propelling themselves. You take so much damage from a grenade jump, that the risk vs. reward for a class that has other methods of self-propulsion isn't as great as it could be.