wiring two 4 ohm dvc subs to mono amp

when wiring two 4 ohm dvc subs to a mono amp do theres 4 speaker slots on the amp +-+- when wiring the subs at 1 ohm do you only use two speaker slots on the amp + - or do you use all +-+- look at this link https://www.the12volt.com/caraudio/woofer_configurations.asp Thanks

Your choice to either wire the subs together to make 1 ohm or to send two 2-ohm connections to the amp.  The amp provides that extra set so that you have the benefit of using the second set if you want to...and it parallels the connection if you use both sets.  A case where you might use both connections on the amp is when you have separate sub boxes, each at 2 ohm (in this case).  The double connection at the amp would make it a 1 ohm load.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.