@luisfernando said:
Wow! I don´t understand why the hell sketchup does that. I mean, it creates a half face in one layer, and the another half in another. There´s no sense.
Thanks a lot guys, mainly Thom for the quick and eficient answers. (Dave too).
Actually Sketchup doesn't do that, you did. Always draw on layer 0. Once a layer is selected, all lines and faces created are on that layer. In this case you must have selected the layers or copied something from another file set to those layers.