MaterialDesignTheme.Thumb.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:local="clr-namespace:MaterialDesignThemes.Wpf">

    <Style x:Key="MaterialDesignThumb" TargetType="{x:Type Thumb}">
        <Setter Property="SnapsToDevicePixels" Value="True" />
        <Setter Property="Padding" Value="8" />
        <Setter Property="Background" Value="Transparent" />
        <Setter Property="OverridesDefaultStyle" Value="True" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Thumb}">
                    <Border x:Name="PART_Border"
                            Padding="{TemplateBinding Padding}"
                            Background="{TemplateBinding Background}"
                            SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key="MaterialDesignGridRowHeaderGripper" TargetType="{x:Type Thumb}" BasedOn="{StaticResource MaterialDesignThumb}">
        <Setter Property="Height" Value="8"/>
        <Setter Property="Cursor" Value="SizeNS"/>
        <Setter Property="Padding" Value="0" />
    </Style>
    
    <Style x:Key="MaterialDesignGridColumnHeaderGripper" TargetType="{x:Type Thumb}" BasedOn="{StaticResource MaterialDesignThumb}">
        <Setter Property="Width" Value="8"/>
        <Setter Property="Cursor" Value="SizeWE"/>
        <Setter Property="Padding" Value="0" />
    </Style>

    <Style x:Key="MaterialDesignGridViewColumnHeaderGripper" TargetType="{x:Type Thumb}" BasedOn="{StaticResource MaterialDesignThumb}">
        <Setter Property="Width" Value="8"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Thumb}">
                    <Border x:Name="PART_Border"
                            Cursor="SizeWE"
                            Padding="{TemplateBinding Padding}"
                            Background="{TemplateBinding Background}"
                            SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</ResourceDictionary>