Courting male fiddler crabs Uca musica sometimes build hoods at the entrances of their burrows to which females come for mating. Females differentially orient to burrows with hoods and thereby show a mate preference for hood builders. Here we describe how this mode of sexual selection may affect hood design and building. Larger males built generally larger but not higher hoods. Small males may build relatively high hoods so that they will be conspicuous to females of all sizes and construction or other costs may limit hood height. Most males built only one hood each biweekly reproductive cycle, typically on a day that many females chose mates, and they finished construction before females began mate searching. Both patterns fit predictions based on applying ideal free theory to the timing of sexual signaling. Sexual selection may favor more frequent hood building but the timing of hood building appears to be optimal.