Umshini wokumba iwuhlelo oludidiyelwe olumba imithombo, njengemithombo kawoyela noma yegesi, endaweni engaphansi komhlaba.
Izinsimbi zokumba zingaba izakhiwo ezinkulu zezindlu ezisetshenziselwa ukumba imithombo kawoyela, noma imithombo yokukhipha igesi yemvelo, izinsimbi zokumba zingasampula amadiphozithi amaminerali angaphansi komhlaba, amatshe okuhlola, izindawo ezibonakalayo zenhlabathi kanye namanzi angaphansi komhlaba, futhi angasetshenziswa ukufaka izinto ezenziwe ngaphansi komhlaba, njengezinsiza ezingaphansi komhlaba, izinsimbi, imigudu noma imithombo. Izinsimbi zokumba zingaba izinto ezihambayo ezigxunyekwe emalolini, amathrekhi noma ama-trailer, noma izindawo eziningi ezihlala unomphela noma ezakhiwe olwandle (njengezinkundla zikawoyela, ezivame ukubizwa ngokuthi 'izinsimbi zokugaya uwoyela wasogwini' ngisho noma zingenayo i-drilling rig).
Izinsimbi zokumba ezincane ukuya kweziphakathi ziyahamba, njengalezo ezisetshenziswa lapho kumbiwa amaminerali, umgodi oqhumayo, imithombo yamanzi kanye nophenyo lwezemvelo. Izinsimbi ezinkulu ziyakwazi ukubhoboza izinkulungwane zamamitha oqweqwe loMhlaba, zisebenzisa "amaphampu odaka" amakhulu ukuzungeza udaka lokumba (slurry) ngokusebenzisa i-drill bit bese ukhuphuka i-casing annulus, ukupholisa nokukhipha "okusika" ngenkathi umthombo ubhobozwa.
Ama-hoists ku-rig angaphakamisa amakhulu amathani amapayipi. Ezinye izinto zokusebenza zingaphoqa i-asidi noma isihlabathi kumadamu ukuze kube lula ukukhipha uwoyela noma igesi yemvelo; futhi ezindaweni ezikude kungaba khona indawo yokuhlala unomphela kanye nokuphakela abasebenzi (okungaba ngaphezu kwekhulu).
Ama-Offshore rigs angase asebenze izinkulungwane zamamayela kude nesizinda sokuhlinzeka ngokushintshana kwabasebenzi okungajwayelekile noma umjikelezo.
Singakwazi ukuhlinzeka ngemishini yokumba ukusuka kumamitha angu-500-9000 ukujula, kokubili kushayelwa itafula elijikelezayo kanye nesistimu yokushayela ephezulu, Kuhlanganisa ne-skid rig, i-track rig efakwe, i-workover rig kanye ne-offshore rig.
