I am new using this program that I considered great! I want to use this program mainly to draw objects to be use with 3D printers. I wonder how can I fix a deformity on a object modified with the solidify tool. Using an extruded vertically mesh circle and then give it depth with the solidify modifier a deformity is shown and I don't know how to get rid of it. Please, give me a hint to solve this anomaly . Thanks in advance.

Try checking the normals. For some reason, the Add>Mesh>Circle has one face whose normals are reversed. When I reversed that one face's normals to face outward like all the rest, the problem was solved.

Please, forgive my ignorance but I looked everywhere and I can't find the "normals" check box. I am using Blender Ver. 2.63. Thanks.

I found it and check "Normals" but the problem persist. I am probably doing something in the wrong order.

First of all you must use a mesh circle and be sure it's not a nurbs circle, etc. (Add>Mesh>Circle).

With the circle selected, go into edit mode. If the properties panel is not displayed, press "n" to display it. (It will be along the right side of your 3d view area). Scroll down until you see "Mesh display". You will probably have to expand it by clicking the black triangle. Scroll down and you'll see "normals" and there are two icons. One (left hand side icon) is for vertices, and the other (right hand one) is for faces. Click the 'faces' icon and you will see little blue lines on each face of your circle mesh. They show the direction of the normals. They all need to point outward. If any faces are pointing inward, select only that (or those) faces and then in the 'mesh tools' panel on the left side of your 3d view, find 'normals' and then 'flip direction'. That will invert the direction of the normals for the selected faces. If the 'mesh tools' panel is not there, press 't' to display it.

Your help was great! Now I can use this feature. I am very grateful. I know there is a long way ahead but I think that bit by bit I'll master it. Thank you again.

Glad I could help you! I know I have asked a lot of questions here and have gotten help from others, so it's nice to give back. Hope you enjoy using Blender!