What are water wrigglers?

[quail kid]

Hello,

Im setting up a homemade incubator for my fridn to put his e ggs.
I just want to know what is a water wiggler for?

Thanks

 

[Sammysmom]

You put the probe from the thermometer in it and it gives you the probable temp of the e-ggs. Helps you know whether or not your temp is correct.