Heat bed holding clamps easy to make.

Simple and cheap DIY clamps to hold the top surface of a print bed
With a thank you for the idea to:-

Sunhokey Improved Glass bed clamp and X-carriage Stability
Suitable for a lot of different types bed surfaces

http://www.thingiverse.com/thing:813458

The build bed:=

Teflon print bed top surface, below is an aluminium sheet with a 24 Volt 300 Watt head pad stuck to it. Below this some cardboard, (for now), that gives space for the heat pad wires. Below this is some thin cork and two more sheets of aluminium with levelling bolts screwing into them.

Video of a how to make these clamps
https://www.youtube.com/watch?v=NbzMLQsa560