It is the lowermost part of a theodolite. It consists of two parallel horizontal plates separated by three leveling screws.

The lower plate with a large threaded hole in its centre is called trivet or foot plate. It provides a means to place the instrument on (tripod) stand and get it screwed. Its central aperture provides a way for suspending a plumb bob.

The upper plate of the leveling head is called the tribrach . It contains a tapered bearing at the centre. It has three arms each carrying a leveling screw. It provides a support for the upper part of the instrument.

The principal use of levelling head is to provide a means for levelling the instrument.

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