Deploy a spikes barrier pressing L. Then you can delete them by pressing L again. If you go to far they will be deleted.
Installation ------------ -Install RagePluginHook(Open Alpha - 0.15.552.2608). You can download it from here: http://ragepluginhook.net/Downloads.aspx -Drop the folder "Plugin" and the file "startup.rphs" inside the main GTA V folder, where GTA5.exe is.