Holder for measuring bed

Holder for measuring level of bed on 3D Printer
Mounting is designed for 3D printer REBEL 2, but i thing it´s compatible with many other printers, or you can draw simple reduction for top part of holder.
For completing this, you need 2pcs M3 nuts, 2pcs screws M3x14(M3x16), one with flat head, and one with countersunk head and one flat washer for M3 screw.

For measuring you can buy cheap tool on eBay, http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=accurate+dial+indicator+0%2C01&_sop=