Solo defensive blocking is fun. Its also hard to do and often not nearly as effective as using the buddy system that people know as building walls in modern derby. Unfortunately, sometimes you partner wanders off to go look at the stegosaurus skeleton in the museum and you're left to fill up the track by yourself. Perhaps you just never had a partner, because your gear smells like a hot pocket full of garbage and despair, either way we'll assume you're all alone and have to stop that speedy bugger with the star...
Really there are three possible places where this is the case as a blocker, behind the pack, in the pack, and ahead of the pack. Here's how I've taken to approaching each scenario with mediocre success:
Behind the pack:
Maybe you're trapped, maybe you like to memorize the opposing team's names & numbers mid-jam, the point is, you are cut off from your teammates and have a job to do (other than getting out of that trap if thats the case... putz) so set up shop when that jammer is about 1/4 lap out.
You're allowed to be 20' away from the edge of the pack, so give yourself that space. Start as far back as you're allowed so you have a couple steps to get up to speed and match the pace of the jammer cruising by, if only for a second. If you're a lot better at positional blocking than I am, then that is an easy one to go for, the hard part is maneuvering yourself infront of the jammer, possibly taking a back-block in the process if you're really lucky. As I'm not the best booty blocker, I tend to bait the jammer to the inside line by leaving a tempting gap, then bodily stepping into the gap as they try for it, knocking them out and dragging them back to the 20' mark before moving. Some jammers will take the cut for the minor, others will refuse and try to come in behind you. Once they've lost their speed jammers are MUCH easier to deal with. Trying for a near-stationary lateral block as they go screaming by isn't gonna cut it, and probably hasn't for the last 2-3 passes. If and when the jammer gets past you (eventually their friends will come knock you out of the running) haul ass towards the front-inside of the pack and make a second try at them, it is surprisingly effective.
In the pack:
Why are you alone surrounded by people? Has the other team so successfully broken up your wall that they have also separated you like chicken parts? Are your teammates are all in the box cause they're more than just awkward touchy? Either way, no dynamic duo action for you, boy-wonder, so put on your big boy pants and get to work.
Hopefully the pack is moving at a decent clip. If it is at a near standstill and you don't have any room to take those couple steps to match pace for a second, you're kinda riding the failbus. Look behind you constantly, but be mindful of offensive blockers lining up to take you out of the equation when their speedy friend comes along. If you see the jammer taking an inside or outside path trough the pack, do your best to plug that exit, hopefully your teammates realize you're doing something and line up to help. Maybe you can even build that wall your coach has been screaming about since the whistle blew... Again, if you're beat, make an effort to get to the front, and by effort I mean sprint!
Ahead of the Pack:
Congratulations, you're winning the turtle race and are in front of the pack! Hopefully you're one of those clever blockers that looks behind them constantly, cause thats where the action is...
Infront I try and go for the opposite approach as the back, almost literally. I try and stay very close to the other opposing blockers at the front, giving me the full 20' to match pace and hopefully slow that jammer down. Positional blocking at the front is a HUGE asset, especially if you can actually plow stop and maneuver at the same time. Be mindful of the engagement zone and listen for your teammates (they can talk, right?) to shout a warning when you are out of play, or about to be. Maybe even call for one of those lazy bums to bridge for you. Knocking the jammer out in the front is great, especially if you can do it right as they approach the apex to try and draw a last-line cut, but not as easily done since they have a wide-open track ahead of them to maneuver into.
Finally, there is one other situation where solo blocking is particularly helpful, but not nearly as common. Hot jammer on jammer action! Jammers can engage each other anywhere on the track, and doing so is often a surprise for the unsuspecting opponent under the star. DeRanged of Rocky Mountain is a prime example. Her positional and impact blocking rival some of the best blockers in the country, something she uses to her advantage.
Good luck, don't go for the huge sweeping hit, and look behind you!