Shortly after 9:30 Tuesday morning, a small hatch opened on the south face of the Washington Monument just beneath its peak, about 550 feet above the ground.

A damp wind blew from the west, and low clouds outlined the dirty white obelisk as passersby began to turn their eyes and cameras skyward.

Then, David Megerle, in a yellow hard hat, blue polo shirt and tan cargo pants, slithered out of the opening. From the ground, he looked like a large bug crawling over the marble “pyramidion” at the top of the monument.

But Megerle was no pest. A senior associate with a prominent engineering firm, he was the advance man of a team of experts that Tuesday began a hair-raising “difficult access” examination of the earthquake-damaged monument.

In a few moments, Megerle, wearing a safety harness and using clips, pulleys and a kind of cloth climbing ladder called an etrier, wove a web of ropes around the tip of the monument to prepare for the team’s inspection descent.

The endeavor is part of an overall examination of the monument in the wake of the 5.8 magnitude earthquake that struck the region on Aug. 23 and has had the structure closed ever since.

The National Park Service said Monday that the monument will be closed indefinitely, until experts assess all the damage and map out a plan for repairs. The interior has already been thoroughly checked.

Tuesday’s effort was the start of the inspection of the exterior. The Park Service said it would take about five days, and a more complete assessment could be finished next month.

The team halted work in mid-afternoon because of the threat of lightning from an approaching thunderstorm, Megerle said afterward.

“There was a storm coming,” he said. “They told us it was 40 miles away, and it was getting near our 30-mile threshold . . . so we decided to retreat. . . . Lightning’s our biggest concern up there.”

He said it was “very cool” to be atop the monument, “a unique place to be” but also “just a day in the life of my job.”

He said the team planned to resume work Wednesday.

Officials said earlier that the quake cracked several of the exterior marble blocks and rained smaller debris, mostly weatherizing mortar, on the ground below.

The monument’s blocks are not held together with any cement, only the pressure of the stones against each other. The Park Service has said the overall structure remains solid, and experts said Monday that they did not think any blocks would have to be replaced.

The monument, technically 555 feet, 5 1 / 8 inches tall, was partly constructed between 1848 and 1854, when it was halted at the 152-foot level. Work resumed in 1879 and finished in 1884, according to the Park Service.

The inspection team, from the Illinois-based firm Wiss, Janney, Elstner Associates, aims to check each of the hundreds of blocks of marble that make up the exterior of the monument.

The inspectors — one for each of the four faces of the monument — plan to descend on ropes, examining the blocks one at a time.

“They’re going to go through every single block . . . take a look at each one,” said National Mall and Memorial Parks spokeswoman Carol Bradley Johnson. The team has access to drawings of the blocks that were done during the monument’s rehabilitation in the 1990s.

They will be able to “find out what has happened because of the earthquake, as opposed to what was there before,” Johnson said.

As Megerle crawled across the tip of the monument Tuesday, tourists, joggers and workers paused to watch.

“All I could think was, ‘He must have a great view,’ ” said Johnson, who was watching from below.

She said she also thought: “Wow, can you imagine telling your kids that you did this? That you were at the top of this incredible landmark? I couldn’t even imagine it, to say nothing of the fact that they should have enormous courage.”