judging size against the window frame, it looks similar to a thing my grandmother used to use for darning socks.
You pull the sock over it and stuff the overhang inside out of the way while darning the hole as required.
might be completely wrong but that is what sprang to mind straight away when I saw it.
CPU- i7 4790K @4.0Gb Cooler- Noctua NH-D15 M/B- Z97 ProGamer P/S- 750W RAM- 16Gb
Graphics- Nvidia GTX970 16Gb Drives- 2x 120Gb SSD Samsung 850EVO, 1x 2Tb HD, 1x DVD-RW
Sound- on M/B Logitec 5.1 surround sound system OS- Win 10 pro , all wrapped in a black Corsair case Display - Panasonic UHD 4k 50" Flatscreen TV.( 3840x2160 Res)