Could you please explain what a spider guard is? Again, laymens terms please.
Thank you both.
The other thread is going up in flames so I figured I would address your question here.
First, the setup. You are on your back and your opponent is on top of you. You can't get out or you would have already. You also have tried whatever pressure point, pinch or gouge you know and it didn't work. You are at the point now where you must survive and minimize damage to yourself.
*I give the above disclaimer because of some people who will no doubt disagree with the very idea of fighting from your back. Ok, with that out of the way...
The Guard position is basically broken down into Closed or Open.
Closed is simple. Your legs are wrapped around your opponents waist and you are trying to smother your opponent's attacks by keeping him close. There are very few finsishes or reversals that will not require you to open your legs. It ends up being a stall position that many people have taken just a bad a beating from.
Enter the Open Guard. Opening the legs enables you to use your shins, knees and feet to push your opponent farther away and increase your margin of safety from strikes. The Spider Guard comes into play when you dominate your opponent's arms at the wrists or elbow and put your shins or feet in the crooks of his biceps. It can wear the guy out trying to punch around or over your legs and baits him into leaning on you which opens opportunities to reverse him. It also creates openings to stomp kick.
Hope this helps.