A knuckle coupler joins two freight railroad cars at the Railroad Museum Of Pennsylvania in Strasburg, Lancaster County Pennsylvania. Each knuckle coupler, depending on the model, weigh between 400 to 700 pounds.

Technical details:
Busch Pressman Model D 4x5 large format press camera.
Graflex Optar 135mm F4.7 lens in a Graphex shutter.
Kodak Ektascan BR/A single-sided X-Ray film shot at ISO 100.
Exposure was 12 seconds at F22.
Developed in Adox Rodinal 1:150 dilution for 5 minutes @ 20 degrees Celsius using Mod54 insert in an older Paterson System Tank # 4 placed on Unicolor Uniroller 352 auto-reversing rotary base.
4x5" negative scanned with Epson V600.