Duarte Paiva helps the homeless by designing lockers to house their things

In Arroios, a neighborhood of Lisbon, stands a set of 12 metal lockers. Surrounded by old trees and newly planted bushes, the lockers represent a pilot project designed by Portuguese architect Duarte Paiva as a way to safeguard the possessions of the homeless.

The shining yellow cabinets also serve as a postal address: Letters can be inserted through an outer slot. Inside, each has three shelves and a place to hang clothes.

Among the beneficiaries is Jorge Toledo. He was the first to receive a key to a locker on Oct. 17, 2013, designated by the United Nations as the International Day for the Eradication of Poverty. Until recently in Locker No. 1 he had put only his "main treasures": photos of his two daughters and a document proving that he is a certified electrician. Now he also stores some clothes, a backpack with other garments, a pair of sneakers, and a tool bag.

Like Mr. Toledo, other less fortunate people use the lockers to store their belongings, which they previously dragged up and down the streets of Lisbon – "the city of seven hills" – in boxes, bags, or supermarket shopping carts.

Now, as winter sets in, they feel protected against robberies and rain.

"The idea is to restore the sense of responsibility of the homeless, reinforce their self-esteem, and reduce the feeling of exclusion and loneliness," explains Mr. Paiva, who in 2007 founded the Associação Conversa Amiga (ACA, or Friendly Talk Association).

The €11,635 ($15,800) locker project was funded by the Lisbon municipal government. Paiva would like to start similar locker projects all over Portugal and in other European cities – and even bring his idea to America.

In order to obtain and keep using a locker a homeless person has to obey several rules, which include maintaining regular contact with the ACA street team, and promising to help keep the area around the lockers clean and not use them to store illicit substances.

In Arroios, the lockers were placed close to a church and police station. It was on the stairs of St. George Church that Toledo used to sleep before being offered shelter in an old van. Sliding open a door of the van's cargo area, he proudly shows his mattress with its crumpled sheets.

Toledo was born in Ilha Terceira, one of the nine islands of the Azores archipelago, an autonomous region of Portugal. His late father, of whom he speaks with visible pride ("Thanks to him, I finished secondary school"), was an aircraft maintenance employee at a US air base there.

Toledo's parents eventually rented their house to a US military officer and moved with their four children (two boys and two girls) to the Azores city of Angra do Heroísmo. Coincidentally, Paiva was born there in 1981.

But Paiva and Toledo never met in the Azores. They first encountered each other in Lisbon in 2010. One year later, the architect was awarded a community prize from Do Something (Portugal), a US organization supporting the charitable projects of younger adults.

Paiva had started volunteering at age 14. His first effort, with the cooperation of firefighters, was "to save a cat trapped on the top of a telephone pole," he says. Instead of being grateful, the animal acted with fury toward his benefactor. That taught Paiva an early lesson.

"This also happens with homeless people – not all of them are docile," he says. "At daytime, they are frequently neglected; at night, when helpers come, they can be aggressive just to reassert their dignity.

"We are not taking care of a homogenous population. There are so many different cases that it is wrong to address them" as though they are all alike, he says.

The ACA has a yearly budget of around €20,000 ($27,000) and about 70 regular volunteers. During 2012 it managed to assist more than 6,100 people – not all of them homeless.

On World Diabetes Day (Nov. 14) a group of ACA volunteers, among them a doctor and a nurse, taught a group of men and women at a senior center the best way to care for their feet. The local Roman Catholic Church, which runs the senior center, is one of 17 ACA partners.

Elsewhere, in a poor neighborhood two young women from ACA were helping a group of children do their homework. Their parents, most of them destitute, pay only a small fee.

Paiva's dedication to the homeless is related to his childhood in the Azores.

"I used to play by inventing and creating things," he says. "My family is not rich, and I had to struggle to have what I wanted, whether it was a toy or a university degree."

When he was 9 years old, he offered bread to an impoverished neighbor, who rejected the gift. Paiva wondered why.

The answer arrived in 2005. It was Christmas Eve. He was delivering food and clothes to the homeless and was surprised when they told him what they needed most: someone to listen to them. They needed a friend.

"My thoughts were, 'I do not have the means to offer a house to everyone, but I can share a portion of my time,' " Paiva says. "Then, I created an Internet page, Um sem-abrigo; Um amigo ["One homeless; One friend"]. Since the beginning our purpose remains the same: to diminish the isolation and marginalization of vulnerable individuals and groups."

He started by offering hot tea to homeless people, still a trademark of ACA volunteers. Every fortnight a different person in each ACA team prepares a large container of hot tea and serves it in paper cups.

One of the six main locations served by ACA is Gare do Oriente. At least 30 homeless people, mostly men, sleep on the cold stone benches of this central railway station, which connects the north and south of Portugal.

All of them are treated like relatives by the ACA helpers, who are easily identified by their green vests.

On a Saturday night, Hugo Martins, a young doctor who has donated backpacks with simple medical supplies for the homeless, gives two octogenarians medical advice. One of them, a widower, owns a house but moved to the station to sleep after the love of his life died five years ago.

The ACA focuses on basic needs, such as offering medical treatment free of charge, obtaining documents, or arranging for a state pension. It does not distribute soup or blankets since many other groups do that.

Working with the homeless is a remarkable personal experience, Dr. Martins says. "I no longer deal solely with diseases but with human beings, who make a better person out of me," he says.

One man always waiting for the ACA volunteers, Armando Barbosa, is unemployed. But thanks to ACA he is now receiving a monthly social services allowance and learning English, and he expects to take the test to become a truck or bus driver. He still goes to the Gare do Oriente train station, where he slept for three months, but now it is only to talk.

Toledo, who received Locker No. 1, says he's never felt "so happy." After two failed marriages and the loss of his father and of two friends, he arrived in Lisbon in 2009, dependent on drugs and expecting to die. "I brought €22,000 [$30,000] and I spent all of it in less than six months on cocaine and parties," he recalls.

Now, sitting in a coffee shop and bakery where he helps out doing a bit of everything in exchange for meals, Toledo smiles at Paiva. He concedes that ACA is "reintegrating him into society." He is saving his money for a journey across North Africa.

Paiva, his friend, is pleased.

"If I cannot change the whole world overnight, I am sure that I can change the street where I live," he says. "Probably, I will never [build] big buildings. But if someone leaves me on an isolated island I will be able to erect a city with [only] a few sticks and ropes."

• For more information, visit http://acamiga​.wix.com/aca-pt or https://www.facebook.com/AssociacaoConversaAmiga (both sites are in Portuguese).

Help the homeless

UniversalGiving helps people give to and volunteer for top-performing charitable organizations worldwide. Projects are vetted by Universal Giving; 100 percent of each donation goes directly to the listed cause.

Below are groups selected by UniversalGiving that help the homeless:

• Let Kids Be Kids Inc. advocates for people who have a desire to be heard but may not have a voice. Project: Provide vital supplies for the homeless.

• Sports Gift offers schools, Scout groups, and other youth organizations a community service opportunity to help the underprivileged. Project: Volunteer to knit gifts for the homeless and others in need.

• Build Change seeks to greatly reduce economic losses, injuries, and deaths from housing collapses caused by earthquakes in developing countries. Project: Support the construction of safe, permanent homes.