Can anyone make a compatibility list for hold the line and stay down for me please? I think they are just stand alone feats am i right? meaning they onlt work with themselves.

And Stay Down! can be used any time the character is performing a close combat attack without using an object, so it is compatible with any other power that uses close combat attacks.
Hold The Line, on the other hand, requires a power action to activate, so it can only be used with powers that do not require their own action, such as super strength or steal energy.

So you can use and stay down with BCF? cool thanks.

As long as you meet the prerequisites, yes. In this case, you need Exploit Weakness along with the Blades.
Heck, if you put it on Sinister Venom you can combine Charge, B/C/F, Exploit Weakness and And Stay Down for a real nasty combo. It's only for a single click, but Venom does qualify for And Stay Down on multiple clicks...

This all sounds deadly.I can;t wait to use both of them.