Q: I'm almost done stringing a racquet and I must have made a mistake measuring the string because it came up short. I'm new at stringing and it took me a while to do this racquet, is there anything I can do to salvage the string job or do I need to pull the strings out and start from scratch?
A: Sorry to hear that happened. I've been there more than a few times, especially when I was still a new stringer myself. Few things are more frustrating than almost finishing a string job and having to go back and start over. Whether or not you can salvage the string job depends on your exact situation.
First of all, did you have enough string to complete the last cross with some left over for the knot, but just not enough to reach the tensioner? If so, your situation isn't terribly dire. The easiest (and probably best) solution is to use a starting clamp—if you have one—with some spare string to act as a "bridge" to the tensioner. If you don't have a starting clamp, you should DEFINITELY invest in one. They're indispensable tools that are useful in several situations, including when you come up short. Starting clamps have saved my butt countless times in similar situations. If you don't have a starting clamp, you can try splicing a scrap piece of string to the end of the string you're trying to tension. It's been quite a long time since I've tried this (since I usually use a starting clamp in this situation), but I have done it in the past with mixed success. Some types of strings lend themselves to this method better than others and you may or may not be able to get your splicing knots to hold while pulling tension.
If you didn't have enough string to complete the job (you're short by a cross or two, for example), my personal recommendation would be to just suck it up and take the extra time to go back and do the job right. Stringing is a craft and like any craftsman, you should take pride in your work and doing the job the right way; trust me, a quality string job is well worth the time and effort you put into it. That being said, there are still technically a few workarounds, but I would NEVER recommend using these on a customer's racquet and you should really only use them on your own racquet in a pinch.
If you're stringing off of a reel or have extra sets of your string lying around, you might be able to just remove your botched crosses and save the mains you've already installed. If you strung two-piece, your mains are already tied off and you can remove your crosses and install new ones. If you strung one-piece, you'll need to move a clamp back to the last main on the long side and cut the first cross, leaving enough to tie off that side of the mains. You can then remove your old crosses and install new ones, ending up with a two-piece string job. Keep in mind that your mains almost always sustain a little bit of wear even if you're careful during installation, so if you go this route you'll be subjecting your mains to some additional wear.
You can also try patching in a piece of string, if and only if you're really desperate for time. This isn't a practice I normally recommend, but if you're ten minutes away from needing your racquet for a tournament match, you might not have any other choice. Tie off what you have and cut another length of string long enough to complete the last few crosses you need. Find a hole large enough, put your new piece of string through and tie a starting knot. Then, weave and tension your remaining crosses and tie off at the end as usual. You may need to carefully enlarge a few holes to accommodate the additional knots—again, not a practice I normally encourage—but it can serve in a pinch.
So, in summary, the "solution" really depends on your circumstances. If you've managed to finish weaving all the crosses and just don't have enough string to reach the tensioner, using a starting clamp as a "bridge" to the tensioner is definitely the best solution. If you didn't have enough string to finish weaving the crosses, your best bet really is to start over so you can provide the highest quality job possible. The other solutions I provided are what I might call "hacks" and really shouldn't be used except under desperate circumstances.
Hopefully that helped! Best of luck.