trampoline
Apparatus made up of a bed stretched by springs; the gymnasts perform acrobatics by jumping and bouncing on it.
safety pad 
Cushioned mat covering the frame to prevent injuries to the gymnast.
bed 
Canvas that is usually made of nylon; the gymnast bounces and performs acrobatic freestyle on it.
frame 
Metal body supporting the bed by means of springs; for competitions, the frame is 3.7 ft above the floor.
spring 
Metal elastic coils that stretch the bed; a trampoline usually has 120 springs.
leg 
Metal structure supporting the trampoline frame.