glider on intersections

HTML

<script src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraphcore.js"></script>
<link rel="stylesheet" href="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph.css">
<div id="jxgbox" style="width: 500px; height: 500px;"></div>

JavaScript

var brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-5,5,5,-5]});
var A = brd.create('point', [-4,-1]);
var B = brd.create('point', [4,-1]);
var li = brd.create('line', [A, B]);
var C = brd.create('glider', [0,-1,li], {fixed:true});