             <td><a class='trait' href='trait.FnBox.html'
                               title='alloc::boxed::FnBox'>FnBox</a></td>
                        <td class='docblock short'>
                            [<em class='stab unstable'>Unstable</em>] <p><code>FnBox</code> is a version of the <code>FnOnce</code> intended for use with boxed
closure objects. The idea is that where one would normally store a
<code>Box&lt;FnOnce()&gt;</code> in a data structure, you should use
<code>Box&lt;FnBox()&gt;</code>.