Entrance, Exit, and a Pencil

Find your way in and out, then take notes. 入 (enter) + 口 (mouth/opening) make 入口 (iriguchi, entrance); swap in 出 (exit) for 出口 (deguchi, exit). And 鉛 + 筆 spell 鉛筆 (enpitsu, pencil) — 筆 literally a writing brush.

口 voices to ぐち in 入口/出口 (rendaku). 入 is い here (入る/入口) but also ニュウ in 入学; 出 is で/だ.す. 鉛 (エン, lead) + 筆 (ヒツ→ピツ, brush) — the small-tsu in 鉛筆 (enpitsu) is the ピツ at work.