It is possible to make a key from a doorknob, but it is not always the most practical solution. There are two main ways in which this can be done. The first is to use a key change kit, which requires the original key to the lock. If you don't have the original key, you can hire a locksmith to make a new one or replace the lock altogether.
The locksmith will need to disassemble the lock and decipher the type of pins and their order in order to create a matching key. The second option is to re-lock the lock yourself using a key change kit and the current key. This process involves removing and replacing pins of different lengths. If you only have one set of keys, it might be wise to get a replacement set made. This is because keys can easily be lost, stolen, or thrown away with the trash. When you have a blank key, it's much easier to make a duplicate as you have the blank piece in front of you and can simply copy it.
The pins contact the driver's pins and align them on the cut line, allowing the plug to rotate and thus open the lock. This works on many different styles of locks, but it can be difficult to figure out how much of a blank key the lock is taking up. Most common door locks can be changed, but if you've lost the original key or the lock is broken, you'll need to change it. A locksmith can decipher the key code and create a matching key if the lock can be disassembled. However, this is an expensive solution to a simple problem: locks and knobs are wasted simply by getting new keys.