New four sided Strop, which side to use?

I've been wanting to get in to learning how to use a straight razor for some time now, and my girlfriend fantastically surprised me with a Dovo Razor and supplies for Christmas.

The strop she gave me looks like a two in one (two strops connected at the top) and being new to this I have no idea which of the four sides to use. There's a smooth black leather side, a black cloth side, a brown soft but textured "hide" like side, and brown slightly rough leather side.

Any suggestions? I know most strops you use both sides, but in this case four is just overwhelming me.
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Most strops are two piece such as what you have, typically a linen and a leather, don't know what material that is but it's mostly just two sides with a back side that's not finished that some will put pastes on, But I,m not really sure what your linen is. Someone might chime in here and help , but go to the library and do some reading on strops, then most of your questions will be answered , then come back and ask what you didn't figure out from there. Plus many videos out there to show you how to strop plus learning how to shave. Tc