Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: Do you have to completly unwind the cord to use it or can you just pull out what you need?
Document: I like this unit. Used the method suggested by other commentators for loading the real - clipping the middle of the 100' extension cord and rolling it up so that both ends of the extension cord are available. This way you can pull out as much extension cord as you need. I wish it had a foot plate - it would be easier to use if mounted on a wall.
It's a good product but you definitely should wait to plug in the cord until after you unwind it since the end will twist as you unravel it from the spool. We use a 50 ft cord with it and it is a good fit.
This is a necessity for the 12 gague ext. cord.You will need to secure the reel (for ease of use).For mobility I used a C clamp onto a 1x12 board and moved it closer to the job.
It is very great product but the design is not that perfect.When you use it(pull out or real back), the "head" of cord is twisting. It won't hurt your cord, only if you take it out from outlet.If there are the product like this onehttp://www.amazon.com/Portacable-Extension-Cord-Reel-Sockets/dp/B000E4ADUYbut you can use your own cord, it would be great.
Have used it several times now and am pleased with performance. I like not having to untangle 100 ft electrical cord each time I use it.I mistakenly plugged cord to wall outlet and then proceeded to pull out cord to use it. That is wrong and really twisted the cord almost mangling the outer covering of the internal wires. My fault. Do not plug in outlet until cord in unwound off the carrier  [or as much of it as you intend using.The handle is uncomfortable.
Tired of spending as much of your work time untangling electric chords as doing the chore? This chord wonder cuts the prep time and does exactly what it says. I have almost 100 feet of chord on my reel to use with my leaf blower/vacuum. Easy to unroll and easy to roll up. One caution. Leave the chord unplugged before you unwind or the chord will get twisted up at the receptacle. After unwinding, then plug it in.
This cord carrier is perfect for my needs. I needed a way to keep a long ethernet cord (250 feet) organized that was easy to wind and unwind. I can wind / unwind as fast as I can walk without the cord getting twisted and knotted.
The best thing about this product is that you do not have to unroll the entire length of cord to get to the plug. Just allow for enough length in the center tube and you won't need to unroll more than you need.
I didn't need to mount this cord carrier, but it comes with a wall template. Very easy to rewind long cords, handle folds in. Lightweight and well made.
This reel is rugged and works very well. It is heavy enough that you can set it down near your work area and pull cord without needing someone to hold the reel. The wall mounts are great for in the garage. The only possible improvement would be sliding contacts so that you can reel out more cord without unpluging.
Answer: You can unwind as much as you need as long as you are using about half the maximum current for the cord on the reel. All properly constructed electric wire, cable and cord is rated for a certain current in air at a certain temperature. If the cord is wrapped up then it cannot release the small amount of joule heat that occurs in the wire, thus raising the temperature and also the resistivity thereby increasing the joule heat  In the summer on a hot day you may technically already be a few degrees above the maximum temperature for the cord even with it unwound so that things could get pretty hot in there with it wound up. To drill a few holes, just pull out the 15 feet you need and don't worry. But for devices that draw 7 or more amps on a 15 amp cord, I pull it all the way out.