- Make a list of non-residential targets to rescue supplies from (with unopposed non-violent hopefully non-destructive entry), before panic buying and looting erupts for supplies, such as shops, hotels, stadiums, garages, tool shops, lumber yards, council depots, hospitals, churches, schools, museums, libraries and theatres.
Once the grid is down, it is up to you to do your own security, medicine and fire fighting and rescue, and to access resources such as medicine, food, equipment and consumables that government illegally failed to distribute, or shelter that councils illegally failed to arrange, so you need capacity for forced entry.
Survivalists are not locksmiths, spies or assassins, so spending time and money on clandestine or non destructive methods of forcible entry is probably a waste, and survivors really only need destructive methods for unopposed entry. Leave the James Bond stuff to security services covert method of entry ‘(CME’) teams. Post-SHTF, noise may not be the problem is used to be, so covert and stealth methods should be unnecessary, other than you do not want to call everyone to come and share the spoils. Some covert techniques are noisy and some overt techniques are silent, for example a lockgun sounds like a bloody hedge trimmer at night yet leaves no trace. Locksmith typically claim a 98% success rate with non destructive entry, so it is not pointless to learn to pick and bypass, you just have other more essential skills to learn around self sufficiency food, water and medicine.
The good news is that components in wall openings are not that strong. Insurance ratings for doors and windows go up to a strength level traditionally known as LPS 1175 SR8, but most manufacturers stop at SR4, to last a few minutes, as above that risk level you need guards instead of extra strength and government ask for a supplementary CPNI (Centre for Protection of National Infrastructure) rating instead. Even SR8 with steel doors held in reinforced concrete by M12 bolts is only supposed to last 20 minutes. And residential products with any SR rating at all are virtually unheard of, at most they tend to be PAS24 rated to slow down silent attack with pocket tools without breaking glass.
SR3 as a wall would be brick, and that can be gouged out to release an opening’s straps and screws, which even for a certified installation could only be with M8s. So essentially not much is going to be harder than that to deal with in itself, unless you are going past (what used to be) guards.
Bear in mind you might to have to go through a curtain wall, rooflights, window bars, grille or shutter, so there can be working at height or sawing through metal. Whichever route, it is easily going to take a few minutes of noise with tools you are not used to and you are not going to just slip in like the movies.