How to hook up monoblocks amp to single mono spkr

Thanks a lot for the advice,
I am using stereo preamp, for this case should I choose the monoblock connected with red interconnect cable from preamp?
 And if I connect one monoblock only, what should I do with the other monoblock? Should I turn it on with black cable connected to preamp?
I am not sure what will be the function of the other interconnect connected to the unused monoblock amp

Am sorry for my dumb question as I can't afford to ruin my amp/speaker if something wrong happen when I experiment with it.

Sorry, missing 1 info, my stereo preamp unfortunatelly doesn't have mono switch

If playing a mono cartridge (most have two sets of outputs where the same signal appears on both the red/green and blue/white set of terminals) into a stereo preamp/system a precise sound-image will appear right between the two speakers.

If you just want to try what it sounds like with a single speaker, just leave one of the mono blocks off and the sound will come from only the side that's left on. If you want to go "Purist" disconnect the interconnect going to the
unused amplifier, that way it'll be easy to go back to normal once you get your curiosity satisfied :-)

You will not be able to hook up both mono blocks to just one speaker unless your speakers are set up for bi-wiring, where one mono block would drive the HF/MF section of the speaker and the other the LF section

Good listening and happy holidays

Peter

Dear Peter, Plato, Onhwy61.
Thanks a lot for the advice.

Happy holidays to you all

Another method is a y adapter, which would be the same as a mono switch.