HostWindow , RadPageView and RadPanel : Remove Borders

Hello, Álvaro,

If I understand you correctly, you have a custom control that is composed of RadPageView and a RadPanel and you would like to remove their borders. In order to do so, you should manage the border visibility per each control. Keep in mind that each control has a different structure, hence different element is responsible for drawing borders around them. For example, in RadPageView you can remove borders by setting the DrawBorder property to false:

//remove RadPageView border
this.radPageView1.ViewElement.DrawBorder = false;

In RadPanel there is a PanelBorder which visibility you can set to Collapsed:

//remove RadPanel border
this.radPanel1.PanelElement.PanelBorder.Visibility = ElementVisibility.Collapsed;

I am also providing my sample project. In case you have further difficulties, feel free to modify it in order to demonstrate the exact setup on your end and get it back to me. Thus, I could be able to inspect the case more precisely and assist you further. In addition, the style of our controls depends on which theme you are using in your application. It would be good to know which is the specific theme that you use. 

I hope this helps. If you have any other questions do not hesitate to contact me.

Regards,
Nadya | Tech Support Engineer
Progress Telerik