I spent some hours on the US side of the wall near San Diego one night in the early 1990s. (Yes there has been a wall there since at least Kennedy’s time.) Crossing the wall was essentially a nighttime activity, but the “Mexicans” (they may have been mostly Mexicans going backwards and forwards between family in Mexico and illegal jobs they had in the USA) seemed to have ladders permanently against the wall on their side. Their heads appeared over the wall well before dark, sometimes waving cockily. After dark the border force vehicles cruised up and down on a road on the US side about 200 metres (in most places) from the wall, trying to guess where the “rushes” would come. Tourists sometimes came to see this nightly game.
(Meanwhile those with the right papers, including thousands legally working in the USA, streamed into the USA via about ten lanes of traffic near San Diego, with 30 second checks of their papers and car-boot.)