...Madaam, nyetu m Black (…Madam, please, give me 'Black.')
...O kwa I nwere Black? (…I hope you have 'Black'?)
...Biko tinyere m ya na Black (…Please put it in 'Black', for me.)

*The above is in the Igbo language. 

These are some of the usual narrative about ‘Black’, in my hometown, in the early and mid 2000s, and possibly today (I no longer live there)

‘Black’ is the local name for the usual light black plastic bag used to package purchased small commodities for customers - here in Nigeria.

The above exchange would usually accompany its’ initial (intended) usage. When a customer asks for ‘Black’, it is understood, even if unspoken that any other type or colour of plastic bag serves OK and is also acceptable.

'Black' comes in two sizes, one slightly smaller than the other. ‘Black’ is granted to a customer, depending not just on the necessity of it, but mainly on the immediate monetary value of the goods that they have purchased.
Storekeepers are known to say things like:

“Is it this 5 Naira worth of pure water that I should put in Black for you?"
"Of course you can easily hold these or take them in your other bag. How much gain am I making in this whole small business anyway?”

This 'Black' gets to form a covering over new purchases, blocking, or postponing consequent excitement from the children at home when an auspicious package comes home. It also tends to check the prying eyes of passers-by alongside their curiosities.

‘Black’ even in its’ tininess and flimsiness is a resolute and absolute wall.
Possessing a huge (littering) presence, it is commonplace, easily accessible; vulnerable; soft; light; weak; susceptible to destruction; simultaneously very useful, and useless, resistant; almost indestructible; inflammable, and possessing a big functional presence.

A 'bag wall', is one component of a particular kind/design of kiln - the down-draught kiln. Its’ function during a firing of ceramic wares is to deflect or/and direct heat to the ‘right’ areas of the kiln, depending on the desire of the ceramist. A simple arrangement of bricks in the path of flame before wares may suffice as a bag wall (sometimes, target bricks are used). 

Like the Biblical walls of Jericho, a bag wall is an object of great significance. Both walls known to be capable of obstructing the paths of joy and of freedom. As well, their fall, and movement away from these paths can make big physical, spiritual, and psychological impacts, like with the wrapping, and the unwrapping of ‘expectations’, from ‘black'.