As far as I understand you want to remove the titlebar of the RadSlidingPane. By design the RadSplitter does not offer removing the titlebar but you can achieve what you need by going through the following steps:
1) set EnableDock="false" for all the sliding panes
2) Include the following CSS in the page's head:
Note the usage of the keyword !important because if you miss it, your custom settings will get overridden by the default ones and you will not get the desired result.
The solution I prepared for you and suggested works fine on my side, let me know whether tit works for you as well. Note, also that I tested with the version you have selected - if you are using a very old version the CSS selectors might be different.
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