[jstn.mrrtt]

im going to quote bills blog on this one:

"Good Morning Teams,

I want to clarify the Game Design Committee’s intention on a few matters to save you time and resources:
1) De-scoring is not permitted (ie. You may not remove game pieces from a trailer)
2) Goal tending is not permitted (ie. You may not block access to a trailer)
3) Don’t spend time attempting to develop a vacuum car system like Jim Hall’s sucker Chaparral car. Even a slight suction over the base of the robot will damage the field surface and you don’t want to do that (See the 2009 FIRST Robotics Competition Manual section 7 rules G-29 & G-30)"

which in essence says NO blocking the trailer, and that it will probably be specified directly in a team update.