ss="type-var">'b</span>)</span> Ctypes_static.structured</span>)</span> <a href="index.html#type-field">field</a></span></code></dt><dt class="spec value" id="val-seal"><a href="#val-seal" class="anchor"></a><code><span class="keyword">val</span> seal : <span><span><span>(<span class="type-var">'a</span>, <span>[&lt; `Struct <span>| `Union</span> ]</span>)</span> Ctypes_static.structured</span> <a href="index.html#type-typ">typ</a></span> <span>&#45;&gt;</span> unit</code></dt><dt class="spec value" id="va