וְה֤וּא יָצָא֙ וַעֲבָדָ֣יו בָּ֔אוּ וַיִּרְא֕וּ וְהִנֵּ֛ה דַּלְת֥וֹת הָעֲלִיָּ֖ה נְעֻל֑וֹת וַיֹּ֣אמְר֔וּ אַ֣ךְ מֵסִ֥יךְ ה֛וּא אֶת־רַגְלָ֖יו בַּחֲדַ֥ר הַמְּקֵרָֽה׃
Ale zaledwie był wyszedł, przybyli sługi jego; gdy zaś spostrzegli, że drzwi komnaty górnej zaryglowane, pomyśleli: zapewne załatwia on potrzebę swoją w komnacie letniej.
Metzudat Zion
It is a euphemism for reliving himself as an Samuel 1:24:3 "And Saul came to relive himself." Its named this based on the way that he is sitting down and facing. To shut in and to cover his legs because of modesty.
Rashi
Relieving himself [lit. 'covering his legs']. Performing his necessary bodily functions. This refers to a bowel movement.12When the legs are covered as a matter of modesty. (Metzudas).