unused block id.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-make_empty_block"><a href="#val-make_empty_block" class="anchor"></a><code><span><span class="keyword">val</span> make_empty_block : <span><span class="optlabel">?block_id</span>:int <span class="arrow">&#45;&gt;</span></span> <span>int <span class="arrow">&#45;&gt;</span></span> <a href="Shape/Type/index.html#type-block">Shape.Type.block</a></span></code></div><div class="spec-doc"><p><code>make_empty_block s</c