A simple example of using WP_Query extensibly.

wp-query-extensible-example.php

<?php
// run a query for the latest 10 jobs.
$jobs = new WP_Query(
	apply_filters(
		'wpmark_job_query_args',
		array(
			'posts_per_page' => 10,
			'post_type       => 'wpmark_job',
		)
	)
);