diff --git a/bedstead.c b/bedstead.c
index 731bc1d..f66c957 100644
--- a/bedstead.c
+++ b/bedstead.c
@@ -1451,6 +1451,10 @@ static struct glyph {
  {{010,010,010,010,010,010,016,000,000}, U(230A) }, /* left floor */
  {{002,002,002,002,002,002,016,000,000}, U(230B) }, /* right floor */
  {{000,000,037,020,020,000,000,000,000}, 0x2310, "revlogicalnot" },
+ {{037,020,020,020,020,000,000,000,000}, U(231C) }, /* top left corner */
+ {{037,001,001,001,001,000,000,000,000}, U(231D) }, /* top right corner */
+ {{000,000,020,020,020,020,037,000,000}, U(231E) }, /* bottom left corner */
+ {{000,000,001,001,001,001,037,000,000}, U(231F) }, /* bottom right corner */
  {{000,000,002,005,004,004,004,004,004}, 0x2320, "integraltp" },
  {{004,004,004,004,004,024,010,000,000}, 0x2321, "integralbt" },
  {{000,037,004,004,004,037,000,000,000}, U(2336) }, /* APL I-beam */