HTML and Sinatra really only support the GET and the POST methods. In order to be able to use the PUT and DELETE methods in Sinatra, you kind of have to "trick" the form to go to the right place. Then you can name the routes the proper way - otherwise you can only really work with GET and POST.
I used the Craiglist Jr challenge for some examples. Let's look at a quick example of a POST form/method/route- in this case, we're creating a new Craigslist article:
POST form and corresponding route:
<form action="/article/new" method="post">
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YOUR FORM FIELDS HERE