The MC1218 launches a 'Falling Block' entity, with the set ID and Data listed on the 3rd line of the sign. Then applies the velocity listed on the fourth line of the sign. (Velocity is relative X:Y:Z)
To get the entity to spawn beneath the launcher, use a negative velocity.
- Third line: Block ID and Data, shows as ID:Data
- Fourth line: Relative Velocity. Shown as X:Y:Z