In the dusty parking lot of this huge Datsun Motor plant two young black men ''armed'' with a bullhorn and a fistful of union membership forms extol the virtues of the ''workers' struggle'' to a wave of exiting black laborers.
This is the front line in the battle to sustain and enhance trade unionism in South Africa - a prime arena of evolving black power in this country.
But it is not a solid battlefront. Black unions are young, fast-growing, inexperienced, harassed by government, and divided on certain fundamental issues.
With a contracting economy putting more pressure on these unions, the divisions are becoming clearer. But there are glimmers of attempts by some of the most important emerging black unions to draw closer together in this hostile economic environment.
''The issues are crystalizing,'' says Taffy Adler, one of the officials trying to organize this Datsun plant near Pretoria on behalf of the National Automobile and Allied Workers Union.
The prominent issue being debated by the unions is what kind of political stance they should take.
They all oppose the Nationalist government, but they appear to be headed in different directions on whether to comply with government regulations, such as the one requiring them to register with the state. Another question is whether to stick to more narrow shop-floor issues or take positions on more wide-ranging labor issues.
There are no final answers on these questions because the union movement is so young. Alliances on particular issues are constantly changing. (The government sanctioned independent black unions in 1979.)
However, close observers see some discernible trends.
On the question of politics, many of the more influential emerging black unions are struggling to chart their own distinct courses, not aligning with popular political movements as have unions in the past. As a result, there is a divergence between the unions and political trends in South Africa's black urban townships.
In the townships, the banned African National Congress (ANC) clearly ''holds the center of gravity'' in terms of general support, says Tom Lodge, a lecturer on black politics at the University of the Witwatersrand.
But many unions, although not hostile to the ANC, ''do not necessarily see it as an organization for workers,'' Mr. Lodge says.
South Africa's largest grouping of emerging black unions is the Federation of South African Trade Unions (FOSATU). At the organization's recent congress, general secretary Joe Foster lauded groups such as the ANC, but said changes in the South African economy had given black workers more importance and set the stage for a distinct workers' movement for the first time. Some union officials talk of building a workers' movement that will be needed even after black rule comes to South Africa.
However, at the same congress, FOSATU committed itself more clearly to certain political goals than in the past. Although it would not affiliate with any political party, it would take part in campaigns toward ''winning political and other rights for workers.''
The evidence of a new political sensitivity by FOSATU, along with its leadership in the brief work stoppage earlier this year that marked the death of white union activist Neil Aggett, has raised the possibility of a rapprochement between FOSATU and some other important unions that previously criticized its avoidance of political issues.
Following several ''unity meetings,'' FOSATU and three other unions - the general workers' union and two food and canning workers' unions - are edging closer together.
It would be an important development if their unity effort succeeds, for unity would bring together the bulk of South Africa's organized black work force into one grouping.
FOSATU and these other unions have been divided in the past not only over political tactics but also over whether black unions should register with the state. All FOSATU member unions are registered.
They have now agreed not to let this issue stand in the way of their joining forces. Combined, they would represent a membership of some 130,000 workers.
''There is definitely a realignment of groups going on,'' says Adler, whose union is part of the FOSATU umbrella.
But a number of unions remain opposed to FOSATU on such key issues as registration, which to some symbolizes co-option with the state.
But divisions that split black workers appear to have been lifted somewhat, leaving the weight of South Africa's black union movement in a more unified stance than in the past. This could bolster the emerging labor union movement as it struggles through the current economic slump.