| E | SK | FIXED CONSTRUCTIONS |
| E21 | USK | EARTH OR ROCK DRILLING; MINING |
| E21 | KL | EARTH OR ROCK DRILLING; MINING |
| E21B | UKL | EARTH OR ROCK DRILLING (mining, quarrying E21C; making shafts, driving galleries or tunnels E21D); OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS [5] |
| E21C | UKL | MINING OR QUARRYING |
| E21D | UKL | SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS (soil-conditioning or soil-stabilising materials C09K 17/00; cutting machines for mining or quarrying E21C; safety devices, transport, rescue, ventilation or drainage E21F) [2, 6] |
| E21F | UKL | SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINAGE IN OR OF MINES OR TUNNELS [2] |