The Target Clip is designed to hold cardboard targets to 0.375” rebar. 
Cardboard with a thickness of 0.100” to 0.125” is recommended. The clip is pushed onto the edge of the cardboard, and then snapped onto the rebar stake. Two rebar stakes and several clips on each side of the cardboard may be required. A board with spacing holes drilled in it is recommended to set the spacing of the rebar. This board rests on the ground.   
Print the clips in the orientation provided, on the large flat side. Three walls and 25% infill is recommended along with a 0.2 MM layer height. Any ridged filament will work.  
-Hoffman Tactical