anchor boy scouts craft danger fibre help hobbies knots rescue restrain restraint rope save strength string support ties barbed wire barbs barrier double fence fencing gray grey metal sharp silvery spirals strands twists wire amarelo bacia bowl contenção drum equipamento fluidos indústria litros lubrificante oficina oil plastic plástico resistência safety segurança tambor vazamento yellow óleo furniture industria industry ladder Step stool stool table tool barricade protection razor wire security security fence barbed black silhouettes sky spiked spikes three strands twisted appearance barbed-tape barbed-wire injury razor-sharp razor-wire security-fence warning