-
This isn't my circular saw, but it's similar and has the same rip fence(?):
Maybe I'm being thick here, but do you just press the base edge of the circular saw up to the strip edge without the guide?
hugo7-
Yes, the guide is only for ripping small pieces off the edge. If you want to rip further into the board you can remove the guide and clamp a long guide to the wood then run the base plate of the saw along the edge of the guide rail. You have to calculate the offset from the edge of the base plate and take that into account when you clamp the guide in place. If you don't need to worry about the cut piece you can screw a guide to it where clamping is a pain.
When you start to get more fussy you realise it's difficult to get a straight guide or one long enough that stays put etc. so the track saw becomes more desirable.
Airhead
By the time you want to make a cut that far into the board you can use a straight piece of timber or better still a rail clamped to the board. Something like a spirit level might work.
Before track saws that's how a lot of carpenters cut sheet goods on site.