機器
background
building
city
concrete
construction
engineering
equipment
ground
heavy
industrial
industry
iron
job
large
laying
light
line
man
master
material
mechanical
metal
mound
new
nut
operation
people
railroad
railway
reconstruction
repair
road
safety
screw
sleepers
spark
steel
technology
tighten
tightening
track
train
tram
transport
transportation
vehicle
work
worker