how to be an effective "runner", to do a crash ball.

to gain ground in rugby is essential and a very good way to do this is through being an "runner" and doing pick and goes's! and what i mean by being an "runner" is where most likely a forward runs on to the ball passed out of a maul/ruck or watever and just runs straight into the line, and a pick and go is just where the balls there after a ruck and a forward just pick the ball up and again runs straight into there line.
these techniques can be used to build up phases, phases are the amount of times in which the ball is recycled back to the same team (through a ruck) without it being stopped through for an example the ball going out or an penalty.

but also another time where being an runner can be used effectively is when the defence may have a hole in it near the ruck/maul, when the defence is unorganised, the team is going back or just simply not expecting a big forward to run at them full pace, this is when its so effective when there not ready for it!

the two times when you use this technique are very different since when your building phases they generally know what you're doing so you won't gain as much ground than if its just a quick one time thing before the scrum half passes it out.

also when building phases you're pack will also generally be more aware of what you're doing so there will be at least 3 of them on your shoulder, although when your a one time runner they should be at least a couple of forwards following close to you anyway, building phases is just a way to keep hammering there defence, because remember its much more tiring to defend than attack.
also when you're doing this, as well as slowly gaining ground you're controlling the ball and the backs can think, and the scrum half can think about how there going to penetrate there defence! also one more thing before i tell you how to do it well is that building up phases will "draw" players in to that concentrated area where you're attacking and then when you ship the ball out its much easier for the backs to beat the defence out wide where there's less of them.
okay so if you're doing this then its quite simple its basically just running hard, fast and low!

but before you make the run there's a few thing you need to think about:
1st) one thing I've learnt is never to get in between the scrumhalf and flyhalfs channel! so to do this all you need to do is drop back deeper than the flyhalf is because remember when your a runner your simply just giving the scrumhalf another option and he may choose to pass it down the line instead which could be the right option, and then you're going get an earful about it from the fly and scrumhalf!
2) also shout as loud as you can! the scrumhalf probably won't be looking for you so you have to shout extra loud to make sure he knows you're there and what you're doing.

so remember when you're actually making the run you also have to think about timing and speed because the point of being a runner is to break through the line or gain ground so you need to be deep (which you should be anyway so your not blocking the scrumhalf's channel) and generally when the scrumhalf is picking up the ball and realises your there you should start running and if he doesn't pass it doesn't matter keep running so you don't block the channel and you'll then just make a good distraction anyway! this is just a general guess on timings on my behalf but i think after a few times you'll be able to time your runs fine by yourself.

now what should you do when you have the ball and your about to go into contact:
1) first of all make sure your running a straight line! but when i stay straight obviously you should run into the gap in between two people but what i mean is don't run sideways and keep your angle at the minimum, this is effective because its hardest to tackle someone straight on, and also you'll slow down if you try and deviate from you line to much.
2) make sure you're running at your top speed and hard, this obviously comes from starting deep but also a mistake some people do is to slow down as they hit them, don't!! speed up!! imagine your going get through them and then your much much more likely to! and also if your running straight into someone then since you should be low with bent knee's (which I'm talking about next) you should go into them and then drive up and in to them! to get the most power when driving up do a little step before you go in, where you go really low and drive up.
3) another important thing is if you're going into them drop your shoulder and get low! you should be going into them with you're shoulder instead of your arms. this is so important, I'll show you! first stand up, put one leg in front of the other like your running then bend your knees, then put your shoulder down so the top of it is pointing forward. now you'll be in such a powerful position! you can even test it if you get someone to push you slightly while standing up, and then when you're in that position, you will see how much more stable you are!

now when you actually hit the player instead of just going okay I'll go down now, instead make sure you stay up and drive with small steps and keep going till your forced down! you'll be surprised how much more ground you can make plus it gives your pack time to catch up and  ruck over when you go down, but if you do all this with good technique, aggression, strength and at the right time you'll be breaking through there line and then you won't be going down quickly then!

also if you want to get an better idea of what building phases is like then check out this video! but this is an extreme example of it and there not really doing it to gain ground but just to waist time so don't actually try and build nearly that many phases but just watch it to get an idea of what phases are!
hope this guide helps, thanks for reading :)