Uneven edges in crochet usually result from faulty technique, whether the application of uneven tension or the misreading of a pattern. However, because going back to redo a particular section would require you to unravel hours of work, you may want to try a less invasive means of correction. While you should examine your work to avoid uneven edges in the future, you can fix the problem at hand and still keep the piece intact.
Things You'll Need
Look closely at the edges to figure out what went wrong. Did you forget to chain one, two or three at the end of a row? Did you skip the last stitch in a row? Did you have too much tension in one row, not enough in another? Did you lose your place when you added a new piece of yarn? Did the yarn itself differ in texture (this occasionally happens, especially in variegated yarn)? Whatever the cause, keep it in mind when you continue this project or start another. Learning from your mistakes will prevent uneven edges and save you a lot of time in the future.
Read the last step of the pattern. Many patterns ask that you single crochet around the entire piece to give the edges a certain uniformity. If this is the case, you may want to finish the piece and add a single crochet border once you have finished. If you can't figure out what you've done wrong, this may be the best option for you in case future rows in the pattern are also uneven. If this is the case, complete your work before you proceed to the next step.
Attach your yarn at the first row of the pattern. Do a single crochet if this row is slightly shorter than the longest row, a double crochet if it is slightly shorter or a slip stitch if it is the same length. If you are unsure of the difference or how tall a stitch will be, stick with the smallest possible stitch, as you can always return. Moreover, if your piece only includes single crochets, a double crochet may be too obvious. Continue to the last row. Return if necessary, then fasten off. Repeat in any other uneven areas. Single crochet around the entire piece if desired.
Always match the yarn to the row you're working on, even if you need to change it several times.
The technique described works best for pieces that are solid, not lacy. If you are doing a lacy piece, you may need to rework the whole piece.