Hello, Jan,
RadScheduler allows you to customize the cell elements by using the CellFormatting event. Thus, you can apply top border to the cells considering the associate time it represents:
private void radScheduler1_CellFormatting(object sender, SchedulerCellEventArgs e)
{
if (e.CellElement.Date.Minute == 0)
{
e.CellElement.BorderBoxStyle = BorderBoxStyle.FourBorders;
e.CellElement.BorderTopWidth = 5;
}
else
{
e.CellElement.ResetValue(LightVisualElement.BorderBoxStyleProperty, ValueResetFlags.Local);
e.CellElement.ResetValue(LightVisualElement.BorderTopWidthProperty, ValueResetFlags.Local);
}
}

I hope this information helps. If you need any further assistance please don't hesitate to contact me.
Regards,
Dess | Tech Support Engineer, Sr.
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