understrap/inc/widgets.php

<?php
function understrap_widgets_init() {
	register_sidebar( array(
		'name'          => __( 'Sidebar', 'understrap' ),
		'id'            => 'sidebar-1',
		'description'   => '',
		'before_widget' => '<aside id="%1$s" class="widget %2$s">',
		'after_widget'  => '</aside>',
		'before_title'  => '<h3 class="widget-title">',
		'after_title'   => '</h3>',
	) );

    register_sidebar( array(
        'name'          => __( 'Hero', 'understrap' ),
        'id'            => 'hero',
        'description'   => '',
        'before_widget' => '<div class="item">',
        'after_widget'  => '</div>',
        'before_title'  => '',
        'after_title'   => '',
    ) );

    register_sidebar( array(
        'name'          => __( 'Off Canvas', 'understrap' ),
        'id'            => 'off-canvas',
        'description'   => '',
        'before_widget' => '<div class="col-md-12">',
        'after_widget'  => '</div>',
        'before_title'  => '',
        'after_title'   => '',
    ) );
}
add_action( 'widgets_init', 'understrap_widgets_init' );