I can't imagine that it would have the slightest effect. If a magnetic pot or pan isn't in direct contact with the induction burner circle nothing occurs.

Are you putting the knives on a backsplash directly behind the induction cooktop? If so, the main problem I see is that grease and splatter will mess up your knives and will require a lot of cleaning. Maybe if you have a powerful overhead vent, that will prevent much splatter and steam born elements from making much mess of your knives.

Ideally, you should put your magnetic knife holder in the area where you you do your chopping and prep work.

Greg

I agree: I'd put tool rails to either side of a cooktop but not behind it.

Our architect suggested rails for a horizontal line (besides function) but we decided that we didn't have enough height in our backsplash to store long tools and didn't want our cabinets any higher to make it work. We installed a magnetic strip in a drawer by the prep sink for knife storage, and we really like it: all the knives are visible for selection, unlike when they were in a knife block, which no longer clutters a countertop. (We used the block in our old kitchen because we didn't have enough drawers & there wasn't a backsplash.)

Regarding the original question, anything metal has to be very close to the induction surface to interact with it.

I'm planning on using the rails not just for knives -- I'll get magnetic hooks to hang utilities like spoons. But yes, the knives will be closer to the sink rather than the cooktop. I'll have four rails that are 2' wide each, and haven't really mapped out placement yet, but I don't think I'll have any behind the cooktop out of concern for grease splatter. We'll see!

thanks!

I have a magnetic pots for spices next to our induction cooktop and they are not affected.

No interference.