CtrEditor/ObjetosSim/ucTransporteGuias.xaml

<UserControl x:Class="CtrEditor.ObjetosSim.ucTransporteGuias"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:CtrEditor.ObjetosSim"
             mc:Ignorable="d"
             d:DesignHeight="300" d:DesignWidth="300">

    <UserControl.Resources>
        <local:MeterToPixelConverter x:Key="MeterToPixelConverter"/>
    </UserControl.Resources>
    
    <Grid>
        <!-- Contenedor principal -->
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <!-- Borde superior -->
        <Border Grid.Row="0" Height="5" Width="{Binding Ancho, Converter={StaticResource MeterToPixelConverter}}" Background="Blue"/>

        <!-- Contenido central -->        
        <local:ucTransporteTTop Grid.Row="1"/>
        
        <!-- Borde inferior -->
        <Border Grid.Row="2" Height="5" Background="Blue"/>
    </Grid>
</UserControl>