It may happen that your edge formed by solid sc, hdc, dc… is not so nice or a bit wavy. Is it loose after washing the piece? Exactly this has happened to me and I was upset about the appearance of my crochet piece. I started to invesitgate and test, and found a solution, that is easy and can be applied to already finished piece. .
From my experience I can recommend to crochet 1 or 2 rows as following
1.row: (sc, ch1, skip 1) repeat on sides, (sc, 2ch, sc) in edges, finish with invisible join
1.row: as above
2.row: (sc in the free sc of 2 rows below, ch1, skip 1) repeat on sides, (sc, 2ch, sc) in edges – finish with invisible join
This row/s needs to be crocheted quite loosely. After I do this edge, I can wash the work in the machine, and it does not change its shape. Every crocheter has its own tension. The above mentioned solution can help you in some extent. If you see that your edge is still not nice, I recommend you unstitch it and crochet it again. Remember, the quality and appearance of your work lies in details!