Aiolos的回答：

看看这个拆装过程图

http://www.google.com.hk/imgres?imgurl= http://www.cqteacher.cn/blog/UploadFiles/2008-10/1028528449.jpg&imgrefurl= http://www.cqteacher.cn/blog/u/littledrops/archives/2008/5956.html&usg=__AHBAVTdZ1siC9Hi2bfrdLfbYF0I=&h=567&w=425&sz=91&hl=zh-CN&start=100&zoom=1&tbnid=8g9Gau01P6ln-M:&tbnh=134&tbnw=100&ei=aVhPTqznNYrKmAWalsz0Bg&prev=/search%3Fq%3D%25E5%25BC%2580%25E5%25A4%25A9m4600%26start%3D80%26hl%3Dzh-CN%26newwindow%3D1%26safe%3Dstrict%26client%3Daff-cs-worldbrowser%26hs%3DAy0%26sa%3DN%26source%3Dlnms%26tbm%3Disch%26prmd%3Divns&itbs=1