filter-spaced-icons.php

<?php
function my_spaced_filter_amenities_icons( $icons ) {
	$icons['spaced_cctv'] = array(
		'id'		=> 'spaced_cctv',
		'icon'		=> 'icon-cctv',
		'label'		=> __( 'CCTV', 'spaced' )
	);
	return $icons;
}
add_filter( 'spaced_filter_amenities_icons', 'my_spaced_filter_amenities_icons' );

function my_spaced_filter_posts_metaboxes( $metaboxes ) {
	$metaboxes['2']['fields'][] = array(
		'ID' 		=> 'spaced_cctv',
		'name' 	=> 'spaced_cctv',
		'title' => 'CCTV',
		'type' 	=> 'checkbox',
		'icon' 	=> 'icon-cctv',
		'class' => 'htp-metafield-third'
	);
	return $metaboxes;
}
add_filter( 'spaced_filter_posts_metaboxes', 'my_spaced_filter_posts_metaboxes' );