Function max_pin_slot 

pub fn max_pin_slot(height: f32) -> u32

The largest pin slot that fits within a shape of the given height while keeping at least a PIN_TOP_MARGIN of clearance below it. Slot s sits at pin_offset_y = top + PIN_TOP_MARGIN + PIN_PITCH * s, so the lowest slot leaving a PIN_TOP_MARGIN above the bottom edge is floor((height - 2 * PIN_TOP_MARGIN) / PIN_PITCH). This is the bound that bounds-checks pin placement (see Block::new_pin_locations).