How do you keep the mouse from falling? Like in this picture: http://www.ergoquest.com/uploads/5/9/1/5/5915120/8821376_orig.jpg http://www.ergoquest.com/uploads

How do you keep the mouse from falling? Like in this picture: http://www.ergoquest.com/uploads/5/9/1/5/5915120/8821376_orig.jpg http://www.ergoquest.com/uploads/5/9/1/5/5915120/8821376_ori...