a couple things to consider when using it...
contact cement needs to be applied to both surfaces.
It needs to dry out a bit before applying both surfaces.
Often, when gluing leather it soaks into the leather and doesn't leave enough on the surface to bond. You may need to apply more than one coat, especially on the flesh (rough) side. It should look shiny but feel dry to the touch.
When you mate the parts, hammer it together while trying to avoid marking the leather with the hammer.
If done properly, the leather will fail before the joint does.
If some gets on the smooth side before dying, it it seems like it always does, let it dry and use a pencil eraser to remove it or it acts like a resist to dye and you will have a big goober looking spot after dying. If you try and wipe it off wet, you will smear it in and you will definitely have a light spot there when dyed.
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