xmlns:scheduleView="http://schemas.telerik.com/2008/xaml/presentation"

<Style x:Key="CustomAppointmentItemStyle" TargetType="scheduleView:AppointmentItem" BasedOn="{StaticResource AppointmentItemBaseStyle}">
    <Setter Property="VerticalContentAlignment" Value="Stretch"/>
</Style>
<scheduleView:OrientedAppointmentItemStyleSelector x:Key="CustomAppointmentItemStyleSelector">
    <scheduleView:OrientedAppointmentItemStyleSelector.AgendaViewStyle>
        <Style TargetType="scheduleView:AppointmentItem" BasedOn="{StaticResource CustomAppointmentItemStyle}">
            <Setter Property="Margin" Value="3 0 3 3"/>
        </Style>
    </scheduleView:OrientedAppointmentItemStyleSelector.AgendaViewStyle>
    <scheduleView:OrientedAppointmentItemStyleSelector.MonthViewStyle>
        <Style TargetType="scheduleView:AppointmentItem" BasedOn="{StaticResource CustomAppointmentItemStyle}">
            <Setter Property="Margin" Value="2 3 1 0"/>
        </Style>
    </scheduleView:OrientedAppointmentItemStyleSelector.MonthViewStyle>
    <scheduleView:OrientedAppointmentItemStyleSelector.HorizontalStyle>
        <Style TargetType="scheduleView:AppointmentItem" BasedOn="{StaticResource CustomAppointmentItemStyle}"/>
    </scheduleView:OrientedAppointmentItemStyleSelector.HorizontalStyle>
    <scheduleView:OrientedAppointmentItemStyleSelector.VerticalStyle>
        <Style TargetType="scheduleView:AppointmentItem" BasedOn="{StaticResource CustomAppointmentItemStyle}">
            <Setter Property="Margin" Value="1"/>
            <Setter Property="ResizeCursor" Value="SizeNS"/>
            <Setter Property="Template" Value="{StaticResource AppointmentItemVerticalControlTemplate}"/>
        </Style>
    </scheduleView:OrientedAppointmentItemStyleSelector.VerticalStyle>
</scheduleView:OrientedAppointmentItemStyleSelector>
<Style TargetType="scheduleView:RadScheduleView" BasedOn="{StaticResource RadScheduleViewStyle}">
    <Setter Property="AppointmentStyleSelector" Value="{StaticResource CustomAppointmentItemStyleSelector}"/>
</Style>