How to stop raspberries from spreading

Rather than corrugated Iron, I used 12" plastic barge board each side of my raspberry bed and it worked a treat. No suckers got through and when I moved the bed the barge board was as good as new ready for huge new bed. Barge board is used to seal the eves in houses and you can get it in Wickes etc.

Now I already have some of that so that may be an idea together with the flower pots