The truth behind the dark humour is
“The barrier was rebuilt between December 2000 and June 2001. A one-kilometer buffer zone was added, in addition to new high technology observation posts. Soldiers were also given new rules of engagement,[14] which, according to Ha'aretz, allow soldiers to fire at anyone seen crawling there at night illegally into Israeli territory.[15] Palestinians attempting to cross the barrier into Israel by stealth have been shot and killed.”
Before the 2005 disengagement Israeli military maintained a one-kilometer buffer zone within Gaza along the border wall which prevented the militants to approach the border, sometimes with gunfire. After the IDF withdrawal the border became easily reachable by the Palestinians.[10] Therefore Israel launched the construction of the enhanced security system along the Gaza border, estimated to cost $220 million and to be completed in mid-2006.[11]
It includes a 7-meter wall with sensors, remote-control machine guns and barbed wire in the three areas where the border runs adjacent to Israeli settlements
The 1km buffer zone is inside the Gaza wall. It borders from there on area where only farmers are allowed to work. They stray over into 1km from the wall no go area and the remote control machine guns do the rest.
https://en.wikipedia.org/wiki/Gaza%E2%80%93Israel_barrier