squaring extrusions to bed

[Cheeto]

Is there some trick to this? All my extrusions are slightly angled inwards, if I get one square the other two are worse. is there any other spots to work with possibly besides the tslot? I'll post some quick pix.

Thanks,
Doug

[Cheeto]

[Cheeto]

How flat should the heated bed be?

[bubbasnow]

I haven't read the manual in a while, are we still squaring the towers to the base before heat bed installation? I don't see the top of the printer but make all your tower adjustments before you put the top on else it will cause more headaches.