Instruction: Generate an answer to the question by utilizing the information contained in the document.

Input:
Question: what is useable area for 24"  magnetic knife tool bar?
Document: This Norpro 24 Inch Magnetic Knife Tool Bar works great and is just what I needed, To replace a wood block.
I have an Ikea brand magnetic knife tool bar, and it easily holds cosmetics like eye shadows with it's magnet. I wanted something similar (but not as long as the Ikea one) for another area, so I got these.Unfortunately, where the Ikea brand version easily holds the cosmetics (they snap into place with a fairly strong attraction), these Norpro magnets do not hold up the metal cosmetics at all. Had to return them.
We purchased this item because we have wall cabinet side panels bordering our kitchen sink area on both sides. Most magnetic knife bars are longer than the standard 12&#34; width of cabinet side panels, but the Norpro fitted perfectly. The item was easy to mount with two screws (included), designed for thickness of knife bar and cabinet side panel.
I bought this tool bar to hold a new set of knives and a pair of shears. It works great. I have it hanging on the side of a wall cabinet by my cooking area. I did not want to put screw holes into the cabinet so I used strong Magic Tape. Looks great!!! !
magnetic knife tool bar does the trick.Easily nailed it up, once close the knives flew to it and they have remained  on the bar till needed  again.
This magnetic knife rack is great. It holds a viriety of knives, from a 4inch paring, to a 8inch slicing knife with ease. The magnets are strong enough to hold the knives but not too strong to where you can't pull them off. For the price, its the best magnetic tool bar!
Since I bought this magnetic knife tool bar, the knife just fell to the floor beside me where I now lay, waiting for the cardamom to oxidize and lose its scent. If you don't suffer from Cardamom-related Spinal Hydroplosion, then this is probably a great product for you.
I was happy to find that this magnetic knife tool bar came in a 12" size. The only convenient spot in our kitchen with free wall space was 13" wide, and it was hard to find something small enough to fit. This is it. I think the hub followed the advice of other reviewers and got longer screws for it, but other than that, it works perfectly.
I have been using my Norpro Magnetic Knife Tool Bar for over a year and will be ordering another one soon. I ordered the smallest one to fit into a tight corner above my countertop. It's a simple design and holds the knives tight. I won't ever go back to using the old dust-catching knife block holder again.
This tool bar works great...holds my knives securely and gives me much needed counter space (no more knife block!). The first one arrived with no screws and when I tried to buy them from hardware stores they didn't carry that size, but Amazon was great and sent me another with the correct screws. 5 stars because Amazon is great and the magnetic knife bar works wonderfully!
Answer: The complete 24 inch area is magnetized and usable.