small gap while drawing i am trying to follow https://www.youtube.com/watch?v=gDJkIu8xvk4&amp;t=655s tutorial to draw basic lime. but there is small gap in center of the lime which you can see . it is very frustrating, what is the worng with me although i follow tutorial carefully?

thanks,
As I said you have vertices overlaying, so select all and press W > Remove Doubles, it will merge these vertices. Also, you need to recalculate the normals because some are flipped, so select all and press ctrN.