---
title: Find a single chain
---

Let's start with a drawing of a rectangle. A rectangle is a model, but we also implicitly know that a rectangle comprises a chain of 4 paths which connect end to end.
Let's find this chain now using <a href="/docs/api/modules/makerjs.model.html#findsinglechain">makerjs.model.findSingleChain(model)</a>:
    
{% highlight javascript %}
//from a rectangle, find a single chain

var makerjs = require('makerjs');

var model = new makerjs.models.Rectangle(100, 50);

var svg = makerjs.exporter.toSVG(model);

document.write(svg);

//now find the chain
var chain = makerjs.model.findSingleChain(model);

document.write('found a chain with ' + chain.links.length + ' links and endless=' + chain.endless);
{% endhighlight %}

<script>
    LiveDoc.evalLastCode();
</script>

Now, let's combine two rectangle models in a union. 
Notice that a chain will continue unconstrained by the fact that the two rectangle models are independent:

{% highlight javascript %}
//combine 2 rectangles

var makerjs = require('makerjs');

var drawing = {
    models: {
        r1: new makerjs.models.Rectangle(100, 50),
        r2: makerjs.model.move(new makerjs.models.Rectangle(100, 50), [50, 25])
    }
};

makerjs.model.combineUnion(drawing.models.r1, drawing.models.r2);

var svg = makerjs.exporter.toSVG(drawing);

document.write(svg);

//now find the chain
var chain = makerjs.model.findSingleChain(drawing);

document.write('found a chain with ' + chain.links.length + ' links and endless=' + chain.endless);
{% endhighlight %}

<script>
    LiveDoc.evalLastCode();
</script>