Suppose, You are an eCommerce service provider. Now you want to accept payment using check. You can use this form/link/iframe/HTML code to collect the payee information.
When the payee fill-up the form and submit it from your website here in onlinecheckwriter you can see his details.
Now you can print checks on his behalf as the payee already permitted you.
But make sure payee information is correct or pay is not fraud before delivering your product.