L21 = 21Mhz
L14 = 14Mhz, etc.....
You can mount elements horizontally or vertically. Note, the manual does not recommend using the 80m element while car is in motion. It is relatively heavy. I recommend putting some Loctite on the antenna set screws since vibration works them loose. In any case check them regularly so nothing falls off. Also recommend tune each element individually before using several at a time.
"Lossy Traps, Oh my!"
"Supporting AMSAT-NA Fox-1 Cubesat Launch in 2013!"