OO gauge loco shed pits

Print out the top and stick it to the bottom using superglue. (designed for printing in PLA with no supports needed). Running a bead of hot glue from a glue stick behind the joint will make it even stronger. Stick some etched drain covers over the holes in the pit base. Cut out track chairs from your chosen track. (I used C&L bullhead - will no doubt will work with others). Stick these in place being careful to align using rails still attached to sleepers to get the spacing correct.  When the glue has dried, slide the rails in place and paint. Install by cutting a suitable hole in your baseboard.