I'm assuming you're using 2 colors? There is a lot of switching back and forth when you do it. You have to make sure the yarn not in use is carried across the back, so you'd knit 2 with one color, leave that yarn in the back, then bring the other color to the front for the purl 2 and bring it to the back before you knit the next 2.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry